In reply to gethin_allen:
Do you mean the Tour of Pembrokeshire which takes place in April?
http://www.tourofpembrokeshire.co.uk/
I've done it for the last two years; though had a bit of a disaster this year and didn't finish.
3 distances 108, 75 & 50 miles. I did the long distance, it's a fairly tough route and this year the conditions were pretty grim.
The organisation and atmosphere are really good though; this year they even had a Mavic support car and motorbike fixing punctures if you were lucky enough for them to pass when you'd stopped.
The entry opens in August and if you entered before the end of the month the fee was only £15; enter before the end of December and it was around £20.
Rob