OK then, the idiots guide to hour building costs in the USA:-
£ 399 airline ticket +£20 to get to LHR
4 weeks cheap motel $39/night = $1932
$ weeks car hire £348
Aircraft (C152) $74 hour 80 hours = $5920
Using todays £/$ rate we get a total of £5713 or an hourly cost of £71.40
As this is just an internet traul I am sure that other incidentals would bump up the pricebut I suspect by no more than £1-2 / hour.
Dane-ger has actualy done the hour building in the UK and Quotes an ALL INCLUSIVE price of £78/hour in an aircraft he discribes as "looking like new". That price drops to £63/hour if you pop across to France.
As you can see the numbers are very close but my guess is that if things go wrong you would stand a much better chance of getting your money back this side of the Atlantic.