If you're willing to travel and book like in the next day or two, Kent medical imaging (west malling, Kent) are doing a January offer where if you book and pay in January, for any date you like, you'll get their 4d scan for £75, reduced from £120ish. You get a DVD of the entire session, a report and also a bunch of regular and 3d photos (meant to be 4 of each type but I walked away with about 25-30 pictures in total!)