BMI			Air Corsica
Lyon				Stansted Gatwick		Manchester		Heathrow
Nimes			Luton East Midlands
Avignon		Southampton Exeter					Edinburgh
Marseille	Birmingham		Stansted Glasgow Dublin Bournemouth Manchester Birmingham	Gatwick Bristol				Heathrow
Bastia									Lyon Marseille Nice
Nice (for Bastia)				Edinburgh Newcastle Belfast Liverpool Bristol Luton Stansted Gatwick

By train: http://www.eurostar.com for trains from London to Valence via Lille.
Also http://www.voyages-sncf.com if you want to split your journey, and for details of trains from Nimes, Avignon and Marseille airports to Valence TGV.

Ferry to Bastia - http://www.corsicaferries.com