Flying from Prestwick with Ryanair couldn't be cheaper...flights as low as 99p! You need to get a train from Brussels but it only costs 10 Euros (I think thats to anywhere in Belgium actually)if you buy from the Ryanair booking office in the airport.
Getting to Oostende couldn't be cheaper. Ryanair do flights from London Stanstead daily, and often for as little 99p!
This is a bit out of date....Ryanair no longer fly to Oostende. They cancelled without telling me!!!
The airport of Oostende, called Bruges International Airport, is just a few minutes drive from the city center.