It is not illegal to park your caravan on the road, but some insurance companies will not be able to insure the caravan if it is stored on the road. If you are parking the caravan on the road it must be lit at night and comply with the other normal parking rules (the nearside must face the pavement so the rear lights are at the rear for approaching traffic).  The caravan should not block anybody’s driveway or create a hazard to other road users, such as blocking visibility around a tight bend.  Some local Councils also take a strong line on the nuisance value of caravans and do, in some cases, take legal action. It’s worth checking with your local authority before parking on the road.
It’s also worth checking the deeds of your home, or any covenants or tenancy agreements to make sure you can store your caravan within your property, as sometimes restrictions can apply.