Hi,
A quick look at the driveLPG website provided the following: Hollyacre, Toddington Lane, Wick, BN17 7PP, Tel. 01903 715715.
My Series 3 (1984) is on LPG too, and as of last year I discovered that I had to get it on 'zee list' - that is the national lpg database. If yours isn't on this list...