Given your stats of 1032.4 miles/27.0mpg down to Wales and back I might have a chance, as add on mine of 690.7 miles/26.9mpg up from Surrey and back (average 41 mph and a slight detour via Cannock on the way up to see some relatives) that looks like a round trip of about 1700 miles, although as I'll be taking a route up through Wales (got to do the Evo triangle again) and a detour to take in some other good driving roads , probably more around 2000 miles. Hence the idea to include a visit to Sunderland - car might need a service, and some bits added if the other 'alf ain't alooking!