From what I read the guaranteed fee was £20 million, plus Villa paid Ipswich the £1.5 million they were entitled to as a sell on fee. Plus a potential £5 million due to us in add-ons.
Presumably they included: Premier League Appearances (eg after 25, 50, 75 etc); Villa retaining their PL status for 1, 2, 3 years; Villa finishing in the top ten/qualifying for Europe provided TM played x number of PL games; England caps.
In that list the most important seem to be a) how often he plays and b) how well Villa do, because that is the best measure of his worth to Villa. So, thinking about it logically, I think the add on for an England cap is likely to be icing on the cake. In other words nearer £100 k than £1 million. Still welcome of course.
And it will be the first time that I can say an England player once petted my dog. Which must be worth something.