Thanks for all of the responses.

I'm relatively new to touring and came into it on the back of occasional, fair weather rides and commuting 7 miles about 3 times a week so my fitness hasn't been the greatest and some people may consider me a 'bike hater' when they see how little care I have put into looking after all of my previous bikes. I have always loved the freedom of having a bike but never much cared for the maintenance until now. Starting again with the components is linked to the changing of my attitude. If I can do this for little cost then great but as Retro Grouch put it - I want to buy my bike a nice present by way of an apology and to show my intention to treat it better.

I have not used all of the gears on the cassette equally, preferring the middle to high cogs, and I definitely favour the high gear on the chain ring. I'm on 700c wheels with Continental Tour Ride tyres. I have limited upper body strength but I prefer a flat bar as it helps me to keep my back straight. A mountain bike accident a couple of years ago left me with a broken neck which, although healed nicely, means I need to pay more attention to my posture in all aspects of life. Drop bars are too much to change as I have found a very comfortable riding position and can go all day without any problems.

I definitely need to change cassette and chain ring and, if a new chain will help with maintenance, then that too but are there any simple visual checks I can do with the derailleurs to check that they are ok before I buy more? I'll take everything apart and give them a clean when I replace the cassette and ring and decide then if I'm going to change them.

Seriously - thanks for all of your responses so far. I had no idea that I'd get to this point with more questions than I had already asked but that is the nature of these forums I guess.