The bubble is bursting in 1 or 2 years??? What? Who told u? LOL - If the bubble is going to burst then why doesn't your girlfriend sell her apartment too? If your plan works (which of course naturally it won't lol) then it means you'll have a load of cash which will be able to buy a big place and your girlfriend will be stuck with her 2 bed apartment which is worth less!!!
Don't get the SL55 by the way - go for the M6. Way cooler.