Arriving at Euston, we managed to hop over to St Pancras when we settled nicely down in the first class compartment. The only wheelchair seats available are in first class, we got served a nice hot breakfast and was in Paris Gare du Nord in a bit over 2 hours.
From there we took the bus to Pompidou Centre (discovering too late, it does not open on a Tuesday) and got on the bus again to continue to Notre Dame.
I unwisely decided that we would eat opposite the Notre Dame and had to pay the premium for the location - it was very expensive for a small plate of plain sphegetti with sauce.
After visiting the Notre Dame, we set off to look for an accessible bateau mouch but did not find one and settle for the Hotel de Ville where we went off to do some shopping. So we went down Rue de Rivoli into BHV just accross and went up to the nice cafe upstairs.