Keith,
Yes you are right, no LPG on the chunnel, I guess most of us Vanners can live with that though given the high prices relative to ferry deals.
I am wondering wether you are an actual user of LPG? I say this because in my experience of manufacturers own systems and conversions they are largley fit and forget, very reliable and needing only simple maintenance operations at long service intervals.
Our familys Dual fuel Vectra is coming up for 80K and has only ever needed visual checks at vitually nil cost, my sons Shogun needed a check at 1k after system instalation and only requires a quick look and filter clean every 20k. The tanks should be inspected every 5 years but this is not a big deal. The injectors are on condition and require no servicing, the vapouriser diaphrams can loose tension but this is a minor routine adjustment and if the filter is a replaceble type it costs pennies and if guaze washable.
Closed loop systems are even better as they have so few components with no digital electronics.
Maybe I'm lucky but I can't see why there should be large service costs, Clive is also a long time user of LPG and I've never heard him talk of big bills - to me Bi fuel is a win win situation. Don't tell everybody though or they will all be using it!