You can definately find a cheaper sexing scan than that. I'd check the internet for places in your area. Some places will do a sexing scan for £90. You might find less?
The problem at ours is local religion popularity, basically a high popularity around Peterborough will choose to abort the child if it is a girl or boy first born. Not sure exactly how it goes as I am not that religion, very annoying as I am penalized over it though