433mhz is getting crowded and there are many other radio users in that bandwidth, the 868Mhz band would be my personal choice as the restrications on how the devices are allowed to operate on there are much tighter than on the 433Mhz. Also close to the 433Mhz band is a ham radio location and with legal output powers of upto 400watts I'm sure if your nearby to one you may have problems despite what the ec guidlines and badges might say. Just got back tonight from quoting for a wireless system, not my prefered choice but the house was impossible to fit a wired system to, and I mean impossible as they want on cables on show whatsoever and in my years of experience there's no way on gods earth of making this happen as it's just be refurbished and has lovely wooden floors upstairs, no loft space and is the worst nightmere I've seen for years. This is always a highly debated topic on here, I'm not for wirefree but from a company and business point of view if it means work and making a profit or loosing to someone else who will install less quality wirefree equipment then we cross the line and will install it. We have very few systems out there but haven't had any problems so far with them so I'd back you on that option. Anyway go for the 868Mhz and any problems you quite welcome to ask for help.