It's becoming a terrible habit, but I have another critter that I haven't been able to identify with twenty minutes of web searching. I've pored over pages full of pictures of UK spiders and Googled "UK spider massive palps" and similar things, but to no avail!
Best current guess is a Lace webbed spider or similar, though I can't find any pictures on which the abdomen looks the same. Still maybe that's just natural variation. I blogged about one of its garden dwelling cousins previously, but this new unidentified specimen was on my study wall. The body was about 10mm long, 20mm including legs (for once I actually held a ruler up to it for a fairly accurate measure).
One thing I did discover in my fruitless research is that the four little spots/indentations on the abdomen are anchor points for internal muscles, there being no skeleton to fulfil that role.