Welcome aboard Damo
If the condition reflects the mileage then I'd say that's a reasonable price. I fitted my Scott Oiler in behind the tail/seat plastic's on the lefthand side (gear change side). Not so easy to adjust as having it in full view, but it means kids can't alter the adjustments either, as you need to remove the seat to do that. I'm afraid I can't offer any advice on the Double Deckers
Chris.