Obvious option is SATA Internacional from LGW or MAN to Ponta Delgada. There are no direct services to Terceira, Santa Maria or the other lesser islands.
Via Germany try Air Berlin over Nürnburg - but that would involve an overnight at the airport hotel both ways (though their rates aren't extortionate compared with airport hotels in UK - even at €1 = £1)
PM me if you would like any more info - we did it ourselves, without a tour operator a couple of years ago).