Lots of good suggestions from you all - and many thanks for your thoughts. Budget is very important and at the moment the Olympus Pen E-PL5 is the slight favourite. Has anyone got any experience of Panasonic cameras?
Rob
Yes, I've been with Panasonic since the introduction of the GF1 and now have a G1, GX7 and G7. It's a bit of a shame that people tend to think of Olympus as the choice for a stills shooter and Panasonic as the choice for video but hey-ho. I shoot only stills with my Panasonic cameras, I always shoot raw and I don't care about art filters or straight out of the camera jpegs.
Of the two newer cameras I have the GX7 is more to my ideal as I like small and unobtrusive kit and when fitted with a compact prime or one of the very compact variable aperture zooms makes a very small and capable package. There seem to be a lot of "kit" lens choices, I have the 14-42mm mega ois lens and it's the size of a prime lens and sharp wide open too. The only flies in the GX7 ointment are that IMO the EVF is poor to hateful but many people seem perfectly ok with it and there's no auto ISO in manual exposure mode. The compact nature of the kit and the swivelling EVF are wonderful though but I just with that the EVF was of a better quality.
The G7 is IMO an absolute star. It's like a little sports car and the EVF is in contrast to that of the GX7 very nice indeed. There are only a few negatives for me, although auto ISO works in manual exposure mode exposure compensation isn't available, I personally find the grip very uncomfortable and...
both the GX7 and G7 suffer shutter shock when used in combination with some lenses between affected shutter speeds. This can be negated with the use of the electronic shutter (which both of these cameras have and indeed the G7 has an auto mechanical/electronic shutter feature which works well) but using the electronic shutter may bring its own issues including rolling shutter which isn't an issue for me and banding under artificial light which is an issue for me. Unfortunately for me the shutter shock issue renders both of these cameras virtually useless when used with a shutter shock affected lens under artificial lighting in the 1/100-1/300 shutter speed range which is of course exactly where I would be if shooting under artificial lighting as the mechanical shutter may give shutter shock and the electronic shutter may give banding. The fix is to not use the affected camera and lens combinations but as this is supposed to be a system this annoys me no end.
On the positive side the cameras are fast and image quality is good. I use mine at all ISO settings up to and including 25,600.
The very latest GX80 and G80 have a different shutter mechanism to reduce shutter shock. Unfortunately the GX80 loses the swiveling EVF of the GX7 and retains the (IMO) woeful field sequential EVF.
Hope that helps.
PS.
Just a little oddity of note...
My GX7 and G7 produce what seems to me to be identical image quality but when reviewing shots on the camera the G7 shots look much nicer and display much less noise at high ISO's. I assume Panasonic does some in camera magic inside the G7 but as I said, once on the PC raw files from my two newer camera are identical.