After much consideration, I decided to go with warrington autogas.
Warrington autogas are not LPGA approved, nor do they pretend to be, but the analogy therin is that "would you pay £200 for a bmw service, when a specialist would do it for £50?".
I had also scoured the web, and found many seemingly independent testimonials from satisfied customers, some of whom were on their second and even third conversion from Andy at Warrington.
I had consulted a local converter (local to where I work, literally a two minute walk), but he seemed very dodgy to talk to, and denigrated Andy at warrington autogas. He also told blatant lies (see this forum post I made http://www.my90.co.uk/lpg/viewtopic.php?t=5681)
He also had what appeared to be a dissatisfied customer on the premises waiting to speak to him after I had left, charged £150 more than Andy at warrington and seemed to have a "have a go" attitude with regard to converting my engine, which didnt seem great.
I also (later) read details of him lying to customers when problems arose with their conversions, blaming the car rather than the conversion. For this reason I decided to take my car the 2 hour round trip to warrington.
Romano, whilst not the most premium kit on the market, are far from budget, so it was decided on one of these kits with a 60 litre tank in the spare wheel well. Although this would cause a bulge in my carpet I wanted itto last as close to a tank of petrol as possible. And as LPG only fills 80% of a volume it is put into (48 litres) and is between 85-95% as efficient as petrol, this was the best compromise.
Anyone who has an Astra Coupe will know that boot space is hardly at a premium (2 full size suitcases and one small, without putting seats down, easily).
The filler cap would be fitted in the rear bumper, to avoid irrepairable damage to the body work of the car.