My currants have been devastated by sawfly larvae this year because I haven't had time to deal with them until recently. When picking them off I came across another kind of creature. It looked superficially like a sawfly larva that has just moulted - very pale yellow and green - but it was thinner and straight bodied, not curled at the end; and and its behaviour was totally different. Instead of waving its head end slowly about, trying to stick to the leaf or curling up and dropping off like a sawfly would, it wriggled very fast and then ran to escape.
I couldn't get a picture, but hope someone might recognise the description. It looked like some kind of caterpillar but I have never seen a caterpillar move so fast. Its movement was very agile, more like a centipede in its speed and manner. I couldn't see how many legs it had but it didn't look like a centipede otherwise.
Update to the above: I found a few more of these larvae today, and realised that they make little "tents" by folding over a leaf using silk. They are slightly wider at the head end (rather like an extremely long thin parsnip or carrot in shape!) and their heads are very pale straw-yellow while the body is pale green. I also found one apparently pupating. It was a latte brown colour and anchored by its tail end while the rest of the body was stretched out straight and off the surface of the (still folded) leaf. It bent slightly when disturbed.
My camer is broken so I'm unable to get a picture. I estimate it was about 1.5 cm long and 2-3 mm wide.