Well, that leaves some questions open, but as I see it you have two options:
-) either fly as originally planned, probably expensive but should work as well as possible; and frankly I'd be surprised you could really get no avgas at EHEH
-) or find an alternate airport, probably closer to your as yet unknown final destination, which does publish avgas availability, and make an intermediate stop for customs. Depending on your as yet unknown point of departure, Calais LFAC could be a strong candidate. Or if flying from the UK's North AND willing to cross a large extent of water , you could check availability of customs at EHTX Texel; that a/d at least has a strong reputation for G/A hospitability.