I think he meant for both petrol and ferry because 600 miles @ 40mpg @ £1.25/l = £85 fuel; + £100 ferry = £185; / 4 = £46 each, so realistically £50 sounds fair. Continental petrol is the same price as here unfortunately, diesel is a bit better though.
It's difficult to say for sure but I believe this is the house (on the east bank), based on the directions description and the fact that there's a brook named "Risdoux" next to it.
It's difficult to say for sure but I believe this is the house (on the east bank), based on the directions description and the fact that there's a brook named "Risdoux" next to it.