The cassette and chain ring have worn quite excessively and the chain is beginning to slip. I want to change everything that may need changing this year at the beginning rather than have a problem in the middle of a ride. I'm planning on riding from John O'Groats to Lands End over 10 days or so in May which, in my current condition, is going to require a lot of training and as I'm doing it on my own, I need to learn how to maintain the bike in case things go wrong while I'm out and about. I don't learn these things particularly easily as I'm not technically minded so having the time to find my way around and put things together from scratch is of enormous benefit to me.

To be honest - I haven't had a problem with the derailleurs apart from the front got a kink in it from what I guess would be a stone chipping up or something like that. I'll need to change them at some point so thought I'd have a crack now while I'm changing the other bits. This is the first time that I've changed components en mass. I had an impression that there was always something better, quicker and longer lasting than what comes on the bike when new and was looking to investigate this.