Also i'm tempted by a Canon FD 50mm f1.8 Olympics edition are they any good?
I'm open to correction but, AFAIK, the the only extra feature of the Olympic lenses was a logo printed on the lens cap.
The FDn 50/1.4 is a fab lens; especially when stopped down a bit (f/2.0 or 2.8) it's razor sharp.
At f/5.6 it will give any lens I own a run for its money in terms of resolving power on my A7, and I'm including a number of EF 'L' zooms, FD 'L' primes and C/Y Contax Zeiss primes in that.
If I'm going out with one lens, it's as likely to be that as anything else.
The 50/1.8 is only single coated and a bit ho hum IMO, though I've shot with it much more on film than digital. It has 5 aperture blade vs 8 on the 1.4 and IME there's little to choose between the FD and FDn versions of the 1.8 in terms of IQ.
Unless you are *really* short of cash, for an extra 20 or 30 quid I'd go for the 1.4 every time.
Edit: I'd say the Zuiko 50/1.8 is a better performer than the FD 1.8, but the FDn 50/1.4 is superior to both.
FWIW, I have heard the OM 50/1.4 is no better than the OM 50/1.8 and not worth the extra expense unless you need f/1.4.