As Florin says it's the Bee beetle, Trichius fasciatus (Coleoptera: Scarabaeidae; Trichiinae). Its UK distribution is broadly Wales these days as seen here on the NBN Map: http://data.nbn.org.uk/interactive/map.jsp?srchSp=NBNSYS0000011551 If seen outside of this area Trichius rosaceus is more likely and is a recent introduction to the UK.
It has to be said that it is a supercalifragilisticexpialidocious find.
It's always worth passing these on - the curent recorder of this group of beetles can be contacted here: http://www.brc.ac.uk/scheme_details.asp?schemeChoice=15
Hi - I am new to the site and can't find out how to post a new blog so apologies for tagging on to yours Alison. I am so excited though that today i wanted to let everyone know i have just seen an enormous flying stag beetle!!