Wales is sadly the most hard done-by in this review, given that it now has to adapt to the English electoral quota when it did not need to do so before (partly because the mountainous and rural nature of much of Wales, combined with relatively poor road connections outside Glamorgan and Gwent, makes large rural constituencies unviable in many cases). It stands to lose 11 constituencies out of 40, varying substantially in size from Arfon (37,733 electors) to Cardiff South & Penarth (72,392, the only in-quota constituency of the 40), and no constituency will survive entirely unchanged. Many smaller constituencies in north Wales (Gwynedd and Clwyd) are not so much abolished as mostly absorbed into (most of) another constituency, Arfon being the clearest case in point.
Each new constituency must be drawn carefully so that proper links can be maintained; luckily the only large wards are in the Welsh capital, Cardiff/Caerdydd and in Swansea/Abertawe. This is particularly problematic in Gogledd Cymru (North Wales), where transport links are poorer (although rural railway lines in Wales overall are much more extensive than those in England; many rural railway lines in England are long since gone by comparison due to the foolish and short-sighted Beeching Axe).
Surprisingly, many of the initial proposals from the BCE in the South of Wales (corresponding to the ancient kingdoms of Glamorgan and Gwent) are rather good, considering the circumstances they have to work in, with some tweaks needed here and there. Cardiff South and East should merely be Cardiff South East and should be closer to the 1950-83 constituency of the same name, and Cardiff North should stay entirely in Cardiff. Reuniting the city of Newport and moving Blackwood into Blaenau Gwent is another idea I approve of.
However, in the north and west, much work needs to be done. Swansea East should not have to extend into Aberavon at all; Aberavon and Abertawe are clearly separate and should remain so. This means Swansea East should absorb the parts of Swansea West that are actually in Swansea, and thus create a united Swansea constituency. No part of Powys should be included in any Dyfed constituency, either, as these two areas lack any real shared interest. Many general ideas (recreating Ceredigion & Pembroke North, reuniting most of Pembrokeshire and Carmarthenshire) should nonetheless stand. Ironically, despite the major changes caused by adaptation to the new quotas, recreating some old constituencies is possible, namely the old Flintshire constituencies (Rhyl and Prestatyn are really in Flintshire, not Denbighshire), and Denbigh. It is worth saying that Ynys Mon, as an island constituency, should have been protected under the 2011 Act as the Isle of Wight, Na h-Eilanan an lar and Orkney & Shetland were, because even though it has a well-used connection via the Menai Bridge it is still separate enough culturally and socially to merit the same protection as other large islands not on the British mainland. Sadly this is not the case, so it will have to expand across said Menai Bridge to the city of Bangor, shifting the rest of Caernarfon into an expanded version of Dwyfor Meirionydd, which Gogledd Sir Faldwyn (northern Montgomeryshire) is better connected to than any part of old Denbighshire. It is another case of 'follow the railway line' which from Welshpool will go all the way to Pwlhelli in the south of Meirionydd. The same should be applied with regards to redrawing the Conwy area and old Denbigh.
Therefore, my alternative constituencies for Wales look like this:
Monmouthshire succeeds Monmouth.
Newport succeeds Newport West, reuniting the city of Newport proper into one constituency for the first time since 1979.
Blaenau Gwent & Blackwood succeeds Blaenau Gwent.
Pontypool succeeds Torfaen; it extends outside the authority of Torfaen and thus should revert back to Pontypool, the name it bore until 1983.
Cardiff South East succeeds Cardiff South, recreating the old Cardiff South East constituency of 1950-83.
Barry & Penarth succeeds the Vale of Glamorgan. Although very similar to the old Barry constituency, Penarth is large enough to be included in the constituency name.
Bridgend & Llantwit succeeds Bridgend.
Ogmore & Aberavon succeeds Ogmore.
Aberdare & Pontypridd succeeds Cynon Valley.
Rhondda & Llantrisant succeeds Rhondda.
Abertawe succeeds Swansea East; note I have used the Cymraeg name for Swansea.
Caerfyrddin succeeds Carmarthen East & Dinefwr, reuniting most of northern Caerfyrddin (Llanelli covers the southern half) again. Dinefwr no longer exists for any official purpose so the name is no longer needed in a constituency.
Pembroke succeeds Preseli Pembrokeshire in practice, reuniting the majority of Sir Benfro. A small western part of Caerfyrddin (Laugharne, specifically) had to be added to it due to electoral quota requirements.
Ceredigion & Fishguard succeeds Ceredigion, effectively recreating Ceredigion & Pembroke North/Ceredigion & Gogledd Sir Benfro.
Brecon, Radnor & Montgomery succeeds Brecon & Radnorshire.
Meirionydd a Trallwng succeeds Dwyfor Meirionydd; (Y) Trallwng is the Welsh name for Welshpool, the largest town in northern Montgomeryshire.
Ynys Mon a Caernarfon succeeds Ynys Mon, taking most of (northern) Caernarfon(shire) in addition to the island of Ynys Mon.
Conwy succeeds Aberconwy, covering most of the Conwy County Borough. Aberconwy no longer exists for any administrative purpose and therefore should be retired as a constituency name.
East Flintshire succeeds Alyn & Deeside and is an exact replica of the 1950-83 constituency of East Flintshire.
West Flintshire succeeds Vale of Clwyd in practice by recreating the 1950-83 constituency of West Flintshire.
Denbigh is a new seat, although it largely replicates the Denbigh constituency of 1918-83.