First steps to owning a motor home

We've decided to make the move from tent to motorhome.There's usually just the 2 of us but we may occasionally want to take 2 guests.  We would like it to 'live' on our drive when not in use.  We live by the sea in West Dorset,  We would like to tour UK and Europe.  We would like to 'wild' park as well as use sites.  We want a used motorhome with a budget under £20k.  Help and advice needed so we don't make beginners mistakes. Thanks.