Hey fella, I think the figure of eight bucks a gallon is way way out of line. Some folks love to put UK down, and sadly some of them are those that were brought up there, which is rather sad, to put it mildly. We don't need 'em!
Our gas at £.75 per litre is about £3.30 per UK gallon, or £2.65 per USG (you see some of the UK knockers don't even know how big a USG is...) and without latest exchange rate to hand - I assume 1.6; equals around $4.20 which is a far cry fron the ludicrous 8 bucks that some numptie suggested above.
At £55,000 per annum you will be over double the national average wage, and so will be comfortably off with modest expenditure, but certainly not in the 3 car 5 bedroom villa class. With a partner adding another £2,000 and no kids I'd say you'd certainly be in the 2 new cars 4 bed villa endless holidays abroad eat out when you like class.
On your figures that is a net income of 39 +24 =£63K pa. = HUGE salary! I'd have thought few BA Capts on high seniority earn that much net...?
You'll be fine!