In reply to James Malloch:
I recently used a newish washer dryer (model in last two years I think) while living with some friends and it seemed good to me. Wouldn't have been able to tell the difference between washing/drying with it vs separate units. It was about £500-600 I think.
It's nice just to be able to put stuff in and set it off for a wash/dry cycle without having to move stuff between the units. Not a big deal obviously but is nice. Not much help if you have lots of clothing you'd typically not put in the dryer though.
The most annoying thing about it was the fact it would take about 20-30min to allow you to open the door during or at the end of a drying cycle, I presume this is a safety feature because it gets hot inside, but it is annoying.
Another annoying thing was that you couldn't set the dryer temperature to 'low' for more delicate or sports stuff, but that seems to be the case for every modern dryer I've looked at. This problem is kind of offset by the fact that the fancy 'fuzzy logic' system stops drying when it can tell your clothes are dry, so doesn't keep on hammering them with more heat until the timer runs out when they're already dry.
I've since moved into a new house and ended up buying two separate units, because there's quite a lot of space. Did quite seriously consider getting a combined washer/dyer though, because it would have been cheaper than what we ended up buying and takes up less space as you say. Went with two separate because I often end up doing several loads of washing in a row because I'm disorganised and because the most economical stand alone tumble dryers can actually be significantly more economical than the tumble dryer in a washer/dyer, which feels nice environmentally and with current electricity rates and depending on how much you use your dryer, it can pay for itself in 5-10 years or so.
Did talk to a few people about washer/dryers before deciding and it seemed like all older (>40) people seemed quite negative on them, possibly a hang over from when they used to be rubbish, or maybe they're just wiser