I went through the same thing with a company called Mario's, 'free' vouchers and photo, with a sale sitting in a dim-lit room with music. ICK. It was horrible and I think it was expensive (didn't buy anything), but maybe not quite as expensive as venture. At least it wasn't a chain, and Mario was the actual photographer.
For prices like these, why not just buy a digital SLR camera, like a canon eos for around £350 (or less maybe on ebay) and take your own photos for the rest of your life! Printing isn't that expensive, and blowing up photos is marginal. You can also find places that blow up photos onto big canvas/pillows, etc. The primrose hill branch - around 1200 for photos? Geez. For that price, buy a camera, go on holiday and get some nice holiday shots yourself... a much better experience all in all. It sounds like venture is screening the people who come in. It sounds like they offer 'free vouchers/photos' but when people who come in look like they won't pay, the photos get 'lost'. Hrmph. Screw 'em. I'd rather either do it myself or give business to locals.
Another idea: go to your local university and find the graphic design/media department and get students to do it for free or for cheap. Then you get people who might be genuinely excited about it, and you'd potentially get shots that are 'artistic'... or take photos you have and love to these people and get them to give them the 'photoshop' treatment. Or buy paintshop pro (a cheaper alternative to photshop) and experiment with photos yourself. All you need is a cheapish scanner or a digital camera and you're set. You can do all sorts of stuff to photos, and as I said before, then get them printed at a shop.
For mothers day last year, my hubby had a photo album made for me, but it's a book, with the photos printed in it. It's a beautiful gift and it cost about £50 using our own photos (which is extensive) at snapfish.co.uk and it was called a memory book, which starts at £20 (www.snapfish.co.uk/storephotobooks), and it's beautiful. I loved it. This isn't the only place ... do some research. Either way, the value is SO much better - a hundred-fold - than venture. After reading this forum thread I will NOT go there on principal.