We have around 650 species of spider in the UK, so it's always fun tracking them down!
I'm tempted to say an
Erigone spp, but there's so many
Linyphiidae it could be that it would be a random guess (we have a lot of the classic 'money spider' - all black, not defining feature etc)
I'd need to see this under a microscope to tell you.
Think the best you'll get would be a
Linyphiidae spp, unless No.9 can throw any ideas at you (no pressure Carl!

)