You can download the latest excel file from here:
http://www.statistics.gov.uk/statbase/Product.asp?vlnk=15282and the Welsh top 100 is in table 3. Sadly English names are far, far more common across the whole of Wales, but in the areas with high concentrations of Welsh speakers, especially North West Wales, there are a lot more Welsh names. (As you can see from these
BAs). And I think the number of Welsh names will increase again as all the kids who were educated in first-language schools - which have been getting more and more popular and widespread - grow up and start having children.
I have actually compiled charts for Welsh name-usage from the current dataset, which I'll post if anyone wants to see them.:)