Thank you everyone for your advice and recommendations.
Oakwood, St.Katherines Farm etc will save a good few bucks, and if I was a frequent flyer I'd be looking at one of these. But it is a very special holiday for us and the first for years, so the ease and convenience (for about fifty quid more) of the multistorey option is going to be my choice.
As an aside, having not travelled for 5 years, and the changes that have come in since due to the B word, how many hours before departure would you recommend arriving at the airport? Thank you in advance for any advice.