Thanks for the responses. I'm aware that my first post here is a bit negative but I needed to vent
In response to some of the comments - I did try before buying...but just a quick run around the bike shop car park - not really enough to find the issues I have found since picking up my actual bike. I was largely going on the reputation for quality - it just never occurred to me I would have an issue. When I discussed it with the guy in the shop he said nobody else had ever complained about anything to do with the Brompton ever and he has sold about 10 a day for the last 40 years (I may be exaggerating slightly). I'm the first person ever in the history of time to not completely love them, he said.
On the wheel flipping 'being the stand' - yeah...I'm aware that's what you are supposed to do with the Brompton. My experience was that it was unstable with the front bag fitted. Maybe it was on uneven ground, although it was just a station platform. But I guess I find it kind of inconvenient that you have to bend down, release a catch then flip the wheel in order to do anything that requires both hands, where I am used to just kicking down a stand.
Someone above mentioned the flexing of the handlebars on the old Bickerton - I actually thought the Brompton handlebars were flexing quite a lot which gave the whole thing a kind of flimsy feel. The clamp that holds the handlebars on doesn't look very sturdy does it? Although I guess it must be ok if nobody else has a problem.
On the fold - I haven't timed it but it's just one of those things that feels like more hassle than it probably actually is. My Tern has two clips that hold it together really well, so the unfold process is: swing bike apart, clip, clip, raise saddle, ride. With the Brompton it's: raise saddle, twiddle, twiddle, twiddle, twiddle, twiddle, twiddle, twiddle, swing bike around, raise handlebars, twiddle, twiddle, twiddle, twiddle, twiddle, twiddle, twiddle, twiddle, flip wheel, fit bag, ride. It just feels like a pain.
I suppose a lot of it is the price - if it cost me the same as my Tern (£300) I'd probably just accept the above irritations as the price for having a smaller fold that doesn't painfully unfold into my genitals at inopportune moments (as the Tern has a tendency to do - main reason for looking at the Brompton). But for over £1000? Jeez. OK, so through cyclescheme this is actually costing me less than £600, but even so.
The guy in the shop says I can return it (-10% 'restocking charge') but I need to see if the cyclescheme can be cancelled. Not sure about that.