Right, Anorak on!
Its very good, but its not close to what is considered "Mint" by collectors. The box has Flee bites, and possibly drawn on? looking at the letter "T" of the Spot On logo?
Decal on the side of the bus is damaged, and also not placed straight, and also a few flea bites in the paint... although it seems nitpicking, these points are very important to its value
What you need to do, is find out whether the variation that you have, is rare, or common, what am I going on about you say? all the decals on the Bus, except the "Ovaltine" logo, are as the bus would have looked back in the day, ie, they were all common to the real full size Bus. Your Ovaltine logo is blue on a Cream background, this could be common, or rare, I simply don't know without researching it, so be aware that a different colour comination may add or subtract significant value!
People who collect, tend to like having ALL variations, of one particular type of model, If you put it up for sale on eBay, make it can be viewed worldwide
So value,
£30-£60 not knowing if its a rare one, and possibly triple that if its a rare variation!
Bottom line though, you'll only get what someone is prepared to pay on the day, as I'm sure you'll already know
Thom