I had exactly the same problem and I solved this week. I bought a spring guide designed for VFC from the brand FPS. I bought it in a Spanish web but surely you will find it in uk. Works perfectly.
https://hobbyexpert.es/interno-guia-muelle-aeg-ver-2-c-rodamiento-fps-gmqd-for-vfc-qd-gearbox-aluminio-21023