There are chestnuts at Greenwich park, Deer Park (Sevenoaks), Greenwich and many more.
It is hard to find describe the exactly location but ask any Chinese person in the UK and they should hopefully tell you.
You will know that you are in the right place when you see lots of Chinese people just as described in the forum posted at the bottom.
If you are lucky you will find lots of chestnuts under the chestnut tree.
All you do is use a screwdriver to help open up the shell or pick the ripe chestnuts on the ground.
What do you do with chestnuts:
As a foodie, I have eaten so many dishes with chestnuts.
My favourite is roasted chestnuts especially during Christmas from traditional chestnut stalls in London which is now a nostalgic thing but can be found at Winter Wonderland or possibly Borough Market.
Mandarin Oriental, Hong Kong gives out chestnuts during the festive season.
Others include chestnut cakes, green tea chestnut loaf from Starbucks, candied chestnut and Brussel sprouts, chestnut butternut squash soup, chestnut stuffing with roast, braised duck with chestnuts.