Anything and everything Spitfire.

Hi, cant remember what happend to my original seat belts.
But am on the look out for some new ones for my mk2 spit.
I keep being asked how long my old ones are, and I simply dont know.
does any one have this info.
Also, how would they be measured?? as they can be adjusted!!!
Piero
Ps what type fitting do they have so I can buy the seat belt fixings (not the bolts, but the other half to the seat belts, the sort bit so to speak)