Where to store caravan - London

Hi, I live in North West London near the North Circular and I would really love to buy myself a caravan for my 40th birthday. I've enjoyed camping over the years but I feel I'd like to upgrade to the next level of comfort. 

My question is can anyone sugest anywhere to park my carvan that is no more than an hour's drive away. I'm thinking around Herts?

Ideally I would like a nice Campsite where I'm based, sometimes staying there as a bolthole from my hectic life, sometimes enjoying some touring when I have more time. 

I don't know how it works as I'm new to this.

Are there sites just outside of London where you can store the caravan throughout the year and if so how much would you expect to pay and can you recomend one?