has a good search volume in the uk. In 2008
findmethecheapest.co.uk sold for 750 GBP.
I was the previous owner of cheaptestgas.co.uk (dropped it)
Couldn't make my mind up whether to take a punt on a DomainLore auction to see if somebody would bite at £50, and ultimately didn't and dropped after 2 years (no inquiries). I found it on an expired domain list too, like you probably did.
By the way what you call 'gas' we would call 'petrol', for us gas = what we use to heat our homes and cook our food. You have a photo of what you would call a 'gas pump' on the domain sale page, which makes no sense to us Brits.... this image would make more sense:
https://fm.cnbc.com/applications/cn.../2013/06/03/100785987-157612903.1910x1000.jpg
I think its one of those which could make somebody some decent money if they whacked up a little comparison script to compare energy tariffs, made a few sales and flipped as a site, but comparison sites + lead gen is not something I'm experienced with and if I was to start in lead gen I probably wouldn't start in such a high competition niche.... I'd break myself in easy, hence why I dropped.
Also, prices from 2008 were basically at their peak for .co.uk domains, bottom fell out of the market after that. Not wise to compare 2008 prices with 2017 prices, I doubt the market will ever hit those heights again.
Probably worth £150 to somebody who churns out turnkey comparison sites and drives traffic to them via adwords + fb ads, if you can be bothered to track them down and offer it to them (which may be more difficult than you think).