Cheers for everyone's input, I have a foot in both camps in terms of buy expensive and buy cheap .... we moved house 15 years ago and I needed a long drill for a particular purpose so bought cheap, it just about did the job I needed it to do and was destroyed at the end of it but would never have been used again since.

The bike however will probably be a keeper so I'd rather save up a bit more and buy "the right one" as hopefully I'll have many years of pleasure from it ....

I did see a comment somewhere though saying that a Sora would likely be more durable than a 105 (I guess the reasoning that they're heavier built / thicker materials) ... does anybody know if that's true as I ride in some pretty horrible conditions through the winter with wet / rain and the inevitable mud on some of the dirt tracks.