my local tkmaxx had a technical westbeach ( high end) jacket in clearnace for £30.!!!that's gotta be at least 200 notes new.
Helmets, wrist guards ( I use skateboarding ones ) are a great idea.
I also wear knee pads and elbow pads ( cheap but decent skateboard/ rollerblade ones) under my clothing to. I should imagine somewhere like sports direct do them cheap.May be even worth looking on argos.
If the weather is foul I wear thin thermal leggings under my pants. I always wear a thermal top under my jacket as a base layer as a minimum.
don't forget to take you wrist guards with you when trying out gloves to see if they fit over them with ease.