I've been noticing a smell of curry sauce when pulling up, today I checked my coolant and it needed topping up slightly. I can smell coolant when the fan is running but cannot find any leaks.

Is it possible its spillage from the service? It had this just before I picked it up about 800 miles ago.

pin hole leaks are very hard to find. Think some one suggested adding food dye to the coolant so it leaves a mark where its leaking. What doesn't kill you is just bidding it's time.