Just thought I would update - went to John Lewis and tried on some Freya and Fantasie bras in 36G and 36GG as well as 34G (the size I had measured myself as) but all far too big in the cup and the fitter also said too big in the band.
So tried a Freya in 34FF and it's a much better fit, although it digs in a bit around the band and under the arms it still feels better than my old stretchy saggy 38E bra and I'm hoping that the digging in will ease once I've worn it for a while. Also tried some Fantasies but they were too big in 34FF but too small both in band and cup in 32F, so not sure they are for me at the moment.
Can't believe I have gone down two band sizes and only up two cup sizes!
So will be looking for some more Freyas and trying out (when my budget allows it) some of the other suggestions on the thread. Could only afford one bra though (normally get two for £20 or similar in M&S) so will need to be looking at Amazon and ebay pronto I think!
Thanks again for this thread and the advice.
PS The John Lewis fitter was really good and helpful and although she didn't measure me she was great at helping work out what fitted best.