What you suggest "Hairdresser in Camden" seriously what phrase would you suggest? Bosh trying saying something constructive or go and troll somewhere else.
Eh? I'm trying to find out what he's offering for the £150? Is he going to promise to give your site the number 1 spot for those phrases for a period of 12 months in the natural listings? Is he guaranteeing a top 10 spot for 12months?
Or is he going to use paid listings to guarantee this spot on the first page? Is he, like Bongo said, going to list your site on another site that ranks well for these phrases. Or is he going to add you to the Google Places, so you list on the map that shows in the results that appears on the page? This is of course, something you can do yourself, for free - and something I'd definitely recommend you do.
These phrases are obviously good phrases to rank for if you think that's what your potential customers might be searching for (which a lot probably are I'd imagine), but will the work this company does bring in more than £150 worth of business for you, giving you a return on your investment. If it will, then it makes some sense to do it. Of course you could also go down a different route and potentially bring in more business, maybe for the same cost (or maybe a little more or less).
I just wondered what he was offering that was different to the others that have contacted you in the past and you were weary of? But it's your business and your money to spend, so best of luck with it and hope it works out well for you.