I was interested that almost all the Welsh people were from Cardiganshire (including Lampeter, county not given) - a distant and not very populous county. Could there be some special connection to Lewisham other than the Greenwich connection mentioned? Before the railways this was a difficult journey whether by land or sea.
Although there are three marriages between Cardiganshire couples, others marry people from elsewhere. And the couples from the county aer not from places near each other - Tresilan is a fair way from Llanbadarnfawr, and the best I can do with Kilgenny is either Kilgetty, Pembrokeshire or Cilgerran, which though also in that county is very near Cardigan town, and at the opposite end of the county. I couldn't make any sense of Llanfynwn, but there's nowhere resembling that anywhere near Blaenporth.
Any ideas? Hugh Jones was from Llanrhydd, Ruthin at the opposite corner of Wales, and his earlier post at Talgarth is in east Brecknockshire.
Thanks for your input Chris, I am not particularly good on Welsh geography, so that is all useful to know! It does seem that the parish, or the area in general may be attracting a significant amount of Welsh immigration, but it would be interesting to perhaps take a sample and see if the children were then baptised in the area, or whether they just married here, and then went back to Wales?
I wonder if the Welsh marriages were connected to the huge numbers of sheep and their drovers that went from wales to London every year.
If you are one of a family of seven or eight there is nothing for you in wales, but the drovers return with tales of the streets of London paved with gold, so you travel with them to seek your fortune.
Mike
Well, I did find (from a 1796 book so contemporary with when we are talking about), that the Earl of Dartmouth who had a large house on the Lewisham side of Blackheath, got permission for two markets a week, and two annual fairs, that used to be three days each, in May and October, and seems to have been for all types of livestock, presumably including sheep

, but by 1796, it was apparently only for cattle and the markets had been discontinued. I did also wonder if Blackheath Common might have been used to graze sheep before taking to the London markets? Maybe Sydenham Common too which was also in the parish? Dulwich Common was also nearby.
https://www.british-history.ac.uk/london-environs/vol4/pp514-536another book from the next year also gives a lot of history of the church, manor, notables etc., and also mentions that in the late 17th century medicinal springs were discovered in Sydenham, in Lewisham parish, known as
Dulwich-wells, which had caused an increase in inhabitants and prosperity for the last 100 years
https://www.british-history.ac.uk/survey-kent/vol1/pp503-526