Thanks very much, Bill.

That's correct. I should have specified that I was talking about K5 Mk1

Basic question, but I can't find an answer. I've used 32GB cards without problems, but I need to get some more cards. I'd like to move to 64GB - will this work?

Thanks very much for the comment - I have got the Magic Lantern K7 book, and it is certainly helpful.

Completely agree about terrible Pentax manuals - my assumption is that they are written by Pentax experts for Pentax experts. The problem is that, presumably because of limited sales, there are no third-party books available, unlike Nikon and Canon. There is an e-book available for the K5, which I thoroughly recommend, by Yvon Bourque, available at http://pentaxdslrs.blogspot.com/. It certainly helped me, although I still struggle with many features of the K5.

I hesitate to expose my ignorance, but after two years use I still do not understand the purpose of the green button on my K5. Old Pentax hands clearly know all about it without being told, but the manual is, to me, completely obscure. The only other guidance I've found so far is in the Magic Lantern book on the K7, which indicates that it simply acts as a point-and-shoot control. I don't expect detailed guidance in the forum, but I would be very grateful if anyone can point me to a suitable source of information.

Haven't had my K5 long enough to comment on the focus question, but I think you will be amazed at the difference that the improved high ISO performance makes. As a non-user of flash, I can get perfectly usable shots now in situations where I wouldn't have bothered to switch the camera on.

Finally gone for the Pentax. What finally tipped the scales was using for the first time the 18-55WR kit lens that came with the K5. It was much sharper and quicker to focus than my old 18-55. So, recognising that there's absolutely no logic to this decision, I came home and immediately ordered the 18-135WR from SRS for £309, as suggested by Exevalley. thanks again for comments.