I think and please correct me if im way off the mark here, but i think its a Long Horn Beetle larvae, certainy the shape/size/markings are similar, but id thought id ask on here to verify this and the species before releasing or squishing it, i know over in East Sussex they have recently felled a massive amount of trees because of the Asian Long Horned Beetle, but it doesnt look right for the Asian Long Horn as it has a different head shape and the body segments look different too.