WAY too expensive. Are you in the city centre of London or something?
You can get 100% cuticle-correct human hair put in by fusion bonding or micro-links for �250 - �350 in a salon, about �150 - �300 by a perfectly reputable and insured home extensionist (is that a word?).
Don't get it braided as it damages your hair and pulls it out, making your own hair sparser at the root and causing patch baldness. The "best" method is the fusion bonding technique, but a lot of people find this irritating and find difficulty washing their hair. It also costs a lot for upkeep - the hair may last 6 months but your own hair will grow and the extensions will loosen and fall out! So you need regular trips to the hairdresser to have loose extensions reattached, etc.
Why not try clip-in extensions? You can buy real hair ones from Sally's, or off the net. They're much more reasonably priced and you can take them out if you hate them. I have my own and nobody even knows it's not my own hair! Take 10 - 20 mins to clip in, and 2 mins to take out. I'd recommend them! x