I had this thing done with the matrix straightening system on 2008.
It cost around 200 quid as well. I had very long, frizzy fuzzy hair, on top of that it was bleached and dyed.
The beautician did a strand test first and showed me how it would look like (she was also testing to see if my hair would fry with all the chemicals). It didn't so I decided to go for it.
It took about 4 or 5 hours but it was sooo worth it. It was silky smooth, flat and freeze free for about 10 months until it began to grow again. I'd highly recommend it.
BTW, if your hair is that long they might charge you much more than that as they might have to use 2 packs of the matrix thingie.