I don't run a Lizard Skin shock-boot on my Trance - is it Tim Flooks (suspension tuning god) that likened it to sand-papering your shock?
If you want a much cheaper chain lube, then get some chain-saw oil. I run a number of chains (SRAMs with the PowerLink are so much easier to split) and the ones I'm not using are kept in oil. Then when I want to use one, I let it drip dry, wipe clean and put on the bike. A litre of chain-saw oil is around £5, which is what you'll pay for 250ml of Finish Line. I still keep a bottle of Finish Line in my toolbox which goes in the car when I'm off riding though. I've got a tube of Finish Line grease as well. Remember GT85 is *not* good as a chain lube - good for getting a nice shine on your frame after washing.
For insurance, does your home contents policy cover it? One of the reasons we went with M&S for our home contents is that it automatically covers bikes kept in a shed or garage up to £4000 without having to declare them or pay an extra premium. I've also got accidental damage cover should I have a big stack and damage my bike. If not, I think the CTC have a recommended insurer.
I'm not a big fan of the Cateye cycle computers, the one I have is a bit iffy. The two Sigma ones I have are much better IMHO.
When out riding, I'd pack a few cable ties, some gaffer tape or electrical tape, Powerlinks for a SRAM chain or a chain rivet if it's a Shimano (though you can make a Powerlink fit), an old toothpaste tube with the lid bit cut off (ideal if you manage to rip a hole in the side wall of your tyre). A good multi-tool will have tyre levers, maybe a chain tool and the right combination of screwdriver heads / allen keys.
For buying stuff, I'd say start with wiggle.co.uk, chainreactioncycles.com and merlincycles.co.uk. If you can find a price better than any of those, it's a good deal IMO.
Finally, get some silver electrical tape or helicoptor tape to protect your frame. I've found the cables rub in certain places on my Trance. From memory:
Cables crossing the seat tube
As they cross the down tube to fit into the guides on the top tube
HTH,
Chris.