There's a problem in identifying Roman churches full stop, as there was only about 80 years between the adoption of Christianity and the 'official' Roman exit (410 AD), so there's not a lot of time to build anything. The monk Gildas, writing in the 6th century, referenced the British Christians as having 'rebuilt churches' so they certainly did exist, but churches might not necessarily be built of stone which makes finding them much more difficult. Bede, a century later, draws on more material in talking about churches which were built during the Roman times (Canterbury, St Albans), and he echoes the material shift from wooden churches to stone ones between the 7th and the 9th centuries. There's a couple of archaeological takes on things (Thomas, Petts), which highlight the problem in determining what qualifies a building as a church. Finding out whether they were extant by the time the Anglo-Saxons got there is a bit more difficult. Virtually all Roman sites were re-occupied by subsequent generations, and churches were built on top of previous sites (the oldest church in Britain, St Martin's is probably built on a martyr's memorial), and after the Anglo-Saxon conversion, churches were built (again), and after the Norman conquest the churches were rebuilt again. Canterbury was destroyed a number of times and they kept rebuilding church, so it's complicated. I count about 8 churches, and about 9 extra-mural/estate churches known from the Roman period, and about 6 baptisteries. It's worth noting that not everything is uncontested.

It's much clearer with the Anglo-Saxon/Norman period. There is a definite excising of English saints and either a destruction or replacing of Anglo-Saxon churches with Norman ones, or incorporating parts of Anglo-Saxon churches into Norman ones (further complicated by the Victorian predilection of rebuilding churches in the Norman style!), however we do have quite a number of Anglo-Saxon churches still around, some still in use. There is an overly-optimistic list here and a more touristy, but more succinct list here.

All of this ignores the 'Celtic' churches of course, and without getting into that argument, there's no Romanesque Welsh churches, but there are some mid to late millennium churches in Ireland.

There's quite a few books on the matter, but here's just a few that I used for this post:

• Petts, David, ‘Christianity in Roman Britain.’, in The Oxford Handbook of Roman Britain., ed. by M. Millett, L. Revell, and A. Moore (Oxford: Oxford University Press, 2016), pp. 660–81 https://doi.org/10.1093/oxfordhb/9780199697731.013.036
• Thomas, Charles, and Charles Christi Thomas, Christianity in Roman Britain to AD 500 (University of California Press, 1981)
• Wood, Ian, ‘The Mission of Augustine of Canterbury to the English’, Speculum, 69 (1994), 1–17 https://doi.org/10.2307/2864782