Kit includes: 30psi Guage, t-piece, 2meters of PVC tubing & a bracket - £29.99
From what I can tell the purple wire is the live feed from the lights, black is the earth, orange and yellow I have no idea.
The PVC hose fits over the nipple on the guage easy but getting it over the t-piece is going to be hard as the t-piece nipple is larger than the hose, might need to heat it to get it to slip over.
The T-piece also comes with a metal bung at one end that has a smal hole in it, I assume this is meant to be in there