Thank you for the input everyone!

To clarify a few points / answer questions;

Before I payed for the bike I was told that they would service it for me the following morning (not that it had already been serviced), and I could then pick it up. As a result I think the service was "part of the deal".

In the absence of the problems I mentioned I'd regard this as good value and convenient purchase for me at this time. Given my budget I really felt that 2nd hand / ex-rental would get me the best quality bike. Living in a remote and rural area of the UK, there are very few LBSes, and most ebay sellers in the country seem to offer "collection only" yet are too far away to make this practicable for me. Wanting a 22.5" frame as a minimum further restricted my 2nd hand buying options. I felt that the apparent good condition of the bike, its relative newness (a 2013 model), the addition of fenders, saddle bag, water bottle holder etc made this a good buy for me at a 33% discount from the rrp / msrp - especially considering that it might take me some time to find another suitable purchase nearby.

I enjoy tinkering with stuff, and learning how stuff works. I've built several high spec PCs and feel the skill set involved isn't wholly divorced from that of bike mechanics. It's been fun trying to fix these problems myself, but feel I should not have been put in this position. I also feel that if this bike requires the wheel to be trued or if the derailleur is bent, then this will be beyond my abilities not to mention tools at the moment. And I want to ride it now!