In reply to Paul Phillips - UKC and UKH:
Good to hear Paul. I was wondering whether it was something like that.
Perhaps you could set it so that only popular photos (eg. 4 or 5 star and/or no. of hits) stay at high res. There are many lesser quality images that could be reduced in size to save bandwidth. Or set it up somehow so most people only see the really good images and the dross ones are mostly ignored. 500px.com seems pretty good in this regard.