Btw reading the thing on depreciation bear in mind second hand bikes dont have VAT on them. New bikes do so if you buy new, you take the hit for the VAT at 17.5%. One reason why theres a fairly hefty depreciation between new and just new.
I think someone said it earlier, if you need money for deposit sell car, pay off the HP and bank that money each month and use the scooter for a while especially if its such a short trip (trips like that wont be kind to your battery and you may find you need to replace a rectifier sooner than youre planning). When you have a fair bit saved for a mortgage get the bigger bike.