I'm currently wearing a 36f. I measure 33.5/34 cms under and 40cms around the fullest part which I think makes me a 34f but when I tried it on it hurt and my boobs were all wrinkled up and out. The m&s lady measured me as a 38f, but I wasn't convinced on her 'fitting' as it felt too loose. Need to buy at m&s as have a load of vouchers to use.
34e as a starting point going by your measurements, but if the cup volume of your 36F fits, so should a 34FF, because if you go down a size in the band, the rule is then to go up a cup size to get the same volume (i.e. a 36F is the sister size of 34FF).
M and S only seem to do one style of bra, so if that doesn't suit your body shape, you're stuffed. Best to get properly fitted at Bravissimo to see how a good fitting bra will fit.