I believe he's still a non-dom so he'll be trying to limit the number of days he spends on UK soil. Same reason he clears off quickly after British F1 each year.
A mate of mine got chatting to Anthony Hamilton in 2007 at the airport in Portugal. His son, Craig (13 at the time) was heavily involved in karting. Anthony took down my friends address saying he'd get Lewis to send Craig a few bits.
My mate thought 'yeah right' but a few weeks later got a hand written card from Lewis wishing him all the best for the future and the usual signed cap, photo etc.
Craig is now an architect living in Edinburgh.
I guess that was all fairly new to Lewis back then. I doubt he would be as attentive now but I know he is heavily involved with animal charities.