Sennheiser RS65s are okay if you absolutely must have cordless. You can get them for £80 or £90. (Click
here for example).
If you could find a second hand pair of the virtually identical RS60s, that might be a bit cheaper.
But these are not even in the same ballpark as the kind of with-cord 'phones you could buy for the same price. That's hardly surprising. You pay for the FM transmitter, FM receiver, modulator, demodulator, rechargeable batteries, battery charger, and portable, battery-powered headphone driving circuitry - it's not surprising that, by the time you've paid for that lot, the 'phones themselves are going to have to be pretty cheap compared with what you could get if all the money were spent on just the 'phones.