4 year old alivio 8 speed rear gears - compatible chain I need to replace my chain (for the first time).  My bike is roughly 4 years old using Alivio 8 speed (24 gears) system.  Looking at wiggle they seem to have 3 chains available.

Looking at other questions on here, (for example Are all 9 speed chains compatible with all 9 speed systems?) it would seem that any 8 speed should work.  

I would like to ask is there a good reason to go for one or another (they all roughly the same price, within a few pounds).

http://www.wiggle.co.uk/?s=shimano+8%20speed%20chain
No, all 8 speed chains are not compatible. For that matter, neither are all 9 speed chains. But for practical purposes, they will be within tolerance to work well enough. Ideal shifting is best obtained with all components being of the same design, in good condition, and good adjustment.

The chains you linked to: There are 2 types of Shimano 8 speed chains. The common one, HG or Hyperglide and IG, or Interglide chains, which are not designed to work together.

If you have HG, and buy a shimano chain, you should get an HG chain.

SRAM chains have looser tolerances, so any 7/8 speed chain will do as well as any other.

I am not saying you can't use any 8 speed chain. Only that some will shift better than others.