Just my thoughts as an unbiased party... you two aren't that far apart on price: 'circa £6,000' and 'nearer £7,000'. Andrew's price seems reasonable considering it's relatively low mileage, the fact it's an SE (a bit heavier but more toys!), recent rear tyres (if Continentals these are about £150 each) and the extra exhaust pipes (the X power ones would probably fetch a fair price if sold on).