Not banter, but just mulling over my next French getaway, hopefully replumbed by then...
Having found Valence - Lille - London - Topsham by train much less stressful than doing the middle bit CDG-BRS by plane, I'm looking at options & prices... I reckon if I got to St P in the evening, stayed in the cheap-but-OK hotel right near the station, caught the early (7.04am) Eurostar to Lille, then the mid-morning TGV to Valence from there, I can do it for £45 + £55 + £50, plus the hotel for about £50. I'd leave Topsham lunchtime, and arrive at my place early evening after the local train (£10) and a walk. Those prices are based on looking at a random mid-week date in March. Timings are actually similar to flight option (longer on the move, but less time needed for safety margin), and prices not wildly different.
Very tempting.