Must say I'm astonished by the depth and detail of the advive from you chaps. Thanks so much. Problem is I'm in almost terminal indecision now. I'm tempted by a 55-300 DA-L I see on offer at SRS for £159, it's more than my budget but if I save up a bit... otherwise there's a 28-200 and a 100-300 on sale from a member here. the 28-200 sounds like it might be a good walk around lens, but then again the 55-300 and 18-55 I already have sounds a fair combination too. I really can't see me carting a heavy and really long lens round very much, but it could be fun to set the tripod up in the dining room and train it on the bird feeder in the garden.

Well thanks for all this. The links are helpful, as are the comments. I guess I'm not what you guys would consider a "serious" birder, and I'm still experimenting. I haven't seen what can be done with image processing on my PC yet and I'll have to invest in some software (another dilemma - what do I need?).
I'd be really chuffed with a shot like Terry's, and as budget is restricted right now I think I'll look out for a cheap pentax 80-300, 55-300 or a Sigma like Terry's on a well known auction site. And i'll be mindful of Gareth's warning. Thanks again to all.

Hi, I'm new to this digital photography lark, so be gentle! I just bought a K200 with the kit lens and want to get a longer zoom for some bird photos. I heard some of the old 35mm lenses will work OK on the K200 so I was hoping to pick something up secondhand, but I'm confused by all the models and letters - F,FA,KF,PZ,DA etc. I don't know which will fit and autofocus. Can anyone please recommend a model I should look out for?

The 18-250 Tamron sounds ideal from what I read here. I wouldn't need to change lens often (if at all), and that aspect appeals. But it's too dear for me and they don't seem to be around secondhand.
Is there an older lens with a reasonably wide range and good image quality that's not too heavy to take on a walk in the woods & which would be less expensive?
All advice gratefully received.