OK Gooseman fair enough, I was being flippant not serious ( I happen to think that Gs ownership is enhanced by not allowing oneself to be bogged down with small details all the time).
But to answer you seriously,
1) Start with the asking price for your (secondhand) 12,000 mile bike which, in your words "would cost £9,000+ from a network dealer" - though you do not actually say that this is what you paid or where you purchased it.
2) Deduct from £9,000+ (or the actual purchase price) the following PC sums:
a) A fuel level sender £......
b) An indicator unit £.........
c) All surface corroded items £............
D) Inconvenience factor £......
Interim value = £............
Add back;
a) Dealer funding of indicator unit £.......
b) Dealer funding of fuel sender £......
c) Value of extra years warranty £.....
d) Dealer funding of replacement surface corroded parts £...
Deduct value of surface corrosion of affected parts (new 2005 under dealer replacement) at a reasonable depreciation per annum until no longer fit for purpose ( has anybody ever reached this point?)
Add back value of the beemer being (your words)
a) "My bike is great, I absolutely love it."
b) "The ride is fantastic".
c) "Without doubt the best bike I have ever owned".
d) " I love my beemer".
When you have finished calculating the above, repeat the exercise for your intended alternative, add up the points, and if your alternative is better, enjoy it and let us all know..
Serious enough for you?
Post results here ............................