Welcome to the forum Simon, you'll find the members on here are a friendly and helpful bunch 🙂
unfortunately However I don't think there are many SQ5 owners in here believe it or not!
serving wise you'll have to factor ni. Costs for the engine, day gearbox and quattro system as they all have different service requirements.
also tyre should be the same on each axle so as not to damage the quattro system babd the tyres should be wearing evenly.
I suspect the SQ5 will have xenon headlights and in which case a bulb can cost you approx £150-£180 to replace.
hope I've helped in.someway.
cheers
Steve