I did it! Although I was quite nervous, it actually went pretty well. The manager said she sensed I'd not been happy or 'been myself' as she put it for awhile...ha! Which is an understatement to say the least. And I left things on good terms, although I really wanted to lay into the management of this place -- they are absolutely horrible! And that's coming from someone who once worked for a coke-head (in the mid-80s of course) -- this has been even worse than that was. It's not a Brit/American thing...just a 'this company' thing.
Anyways, I'm encouraged...onwards & upwards. I've got the interview a week from Tuesday, among other prospects I'm looking into. Worst case scenario, I end up doing house frau duty again for awhile. But if nothing else, I'll go back to temping until the right permanent opportunity comes up.
In resigning, I just spun it in terms of 'this job is just not right for me'...'I don't see myself continuing a career in this particular field'...etc (UK pensions industry)

I am still planning to work out my notice period (one month) but they said (since I'm still in early months there) if I needed to leave sooner, that I probably could.
Thanks again for everyone's support!
PS -- All the other people on my team, who are just as miserable there as I am which tells you a lot, were so chuffed that I just up & quit. DH says I might start a trend...it's gonna be like 'The Great Escape'. I said yeah -- you know in Chicken Run, it was the American chicken who came & helped the British chickens break out of the coop. LOL