I don't think reliability should be an issue of concern. Any forum member would buy that thing with your eyes wide open. The majority of reliability issues would be the same as any P38.
You have the addded bonus that this was an officially approved modification. I believe the engine and tranny were upgraded as part of the mod (source RR.net, not the add).
Honestly, I don't know the guy from adam so I've no agenda or I'm not trying to promote it but if LPG was cheap in Ireland I'd be after that like a shot. Its got rarity value alone, look at the numpties advertising their RRSport lookalikes ofr 9 and 10 grand for what is effectively a hacked up motor. This thing is the genuine article with only a couple made in RHD form.
I paid £6,000 for my 98my DSE a few years back so it looks a steal to me.