From what I know and from reading posts on http://www.lpgforum.co.uk it's a reasonable kit if fitted correctly but it's very sensitive.
FWIW I would highly recommend the motogas kit that I and many others have fitted. It is proven to work on the Omega time and time again and the support is good, both here and from the supplier. There is no reason why you couldn't source the tank elsewhere, if this is what makes the kit price high, if you so desired.
Just my opinion

Agreed. We must have collectively put quite a few miles on that kit by now so I see mno reason to go elsewhere. I'd also be surprised if it's not the cheapest, TBH. IRO 700 quid for a V6 kit, 4 hole tank and all parts for installation takes some beating...
Kevin
Cheers Guys, glad I asked the question -
is this the kit that U-FIT LPG is selling on Ebay?
If so how much would I expect to pay for the biggest cylindrical tank that would fit across the rear of the back seats in the boot, 80litre I think? :-/
It is, although if you PM Lazydocker he will be able to furnish you with details of the supplier, who gives discount to OOF members, IIRC.
My tank is an 80 litre and there's loads of space around it. You could certainly fit a 90 litre, probably a 100 litre tank if you really needed the capacity. My kit was IRO 700 quid inc VAT delivered including the tank. Not sure how the cost of the tank breaks down.
That's a 4 hole tank too. Probably a wise move if you're going for a 100 litre as they fill much quicker.
Kevin
It is the same one... The guy I've got details for is the chap who was actually supplying the kit for Jeremy at U-Fit. The whole thing is absolutely superb and really suits the Omega well

I've got a 90L tank fitted but it was a bit of a pain to mount the frame... I had to have the tank inside the frame to slide it under the Bose amp but I think you'll be OK with a CDX :-/ :-/ Anyway, the 90L it a 400mm diameter tank, the same as a 100L, so all you'd have to do is check the length. I'm fairly sure I've heard of someone who's got a 100L tank fitted and as long as you don't require access to the sides you'd be fine.
As for the single/4-hole tank discussion there's a couple of ways to look at it... A 4-hole is more expensive but will fill more quickly. A single hole tank with multi-valve will work out quite a bit cheaper (I believe) and will be perfectly adequate for the 2.2 power output but will fill more slowly! On my Rangie I had 2x30L 4 hole tanks and an 80L single hole... It still filled all of them from empty in around 5 mins IIRC. LPG pumps fill at different rates from garage to garage so best advice is to decide whether you have the patience to wait for a single hole to fill. I went for a 4-hole purely due to the power requirement being perilously close to the maximum capability of a single hole tank and do a lot of towing

TBH, if you can cope with having a slightly lower range I'd advise the 80L tank as the fitting of the frame will be so much easier and it'll leave you slightly more boot space available. Don't forget that the tank size quoted is water capacity and in reality it's only 80% of that capacity that you can use for LPG so a 100L tank is only 80L usable, and an 80L tank is only about 64L.
I think you've got the details for the guy to contact but if not then PM me and I'll send them over. I know he's been a bit difficult to contact lately but things should be sorted now.