They where £12 at my local boots check boots clearance bit people
Got one - works wonderfully. Bought another so I don't have to keep moving the one I have from the living room to the kitchen. Wonder if you can buy an extra receiver with these.. hmm. Also note - if you're in no rush for one of these (e.g. when forward planning) Lidl has these off and on for slightly cheaper. That's where I got the first one.
Currently in Tesco for £16.50 also
Had one of these for 6 years and travelled around the world with it, works perfectly. Had all the most expensive kits but they all broke in the end (but totally understand why people want a cam when you have a tiny baby, I did too).