'I will also provide backlinking for 5 keywords to improve the search engine ranking of the site for those.
This is posting on forums / press release websites with relevant links etc.. to help google “find” your site.'
Press releases I'm OK with. The other stuff is a bit risky for a newish site. The phrase "provide backlinking for 5 keywords" suggests a lot of keyword rich anchor text which is likely to trip a Penguin (over optimisation) penalty.
£650 is not the problem. It's what you are getting for that money that is iffy.
What worries me is that someone has, in this day and age, made a site that has white writing on a black background. Any big agency tests I've seen in the past have found it gets half the readership compared to black on white. The only exceptions were for overhead projector slides and theatre programs. It makes it hard on the eyes.
ps Where has Wynne's really good post about social stuff / local gone?