Just an update chaps. I phoned Virgin after seeing the advice in this thread.
I told them I did not have a dual band phone and I was told their SIM wouldn't work in my phone then.
However, I said in that case I'll have to buy one of your phones. I was told " oh don't do that, if you hang on and check back with us, probably before the end of May we'll be announcing news that will interest phome users like you"
I think it was very sporting of Virgin to "tip me the wink" as it were. The very nice girl also told me to check out all the prices as the competition were dropping prices all around.
So if any of you don't have dual band but would like to buy just the Virgin sim, we may be in luck soon!