The majority of Belfast is in County Antrim and the towns of Portrush, Portballintrae, Ballycastle, Carrickfergus, Cushendun, Cushendall, Waterfoot, Carnlough, Glenarm and Whitehead on Belfast Lough. The county town is Antrim.

Antrim and Newtownabbey Borough Council.

There is no mention of motorhomes or even car parks.

Mid and East Antrim Borough Council

Includes the towns of Carrickfergus, Ballymena and Larne.

Causeway Coast and Glens Borough Council

Includes the towns of Ballycastle, Ballymoney, Bushmills (home to the worlds oldest distillery), Castlerock, Coleraine, Limavady, Portrush and Waterfoot.
There is a list of car parks a lot of which are free.

Belfast City Council

There is no mention of motorhomes but there is a list of car parks, many of which are free but no mention of height barriers.

Lisburn and Castlereagh District Council

Towns include Aghalee, Annahilt, Dunmurry, Drumbo, Dromara, Glenavy, Hillsborough, Lisburn, Maghaberry and Moira.
There is no mention of motorhomes on the website and neither is there mention of car parks.

Giants Causeway - use the Bushmills car park.

Portrush - Sandhill Drive Motorhome Park is situated within easy walking distance of the town centre and both East and West Strand. Motorhome parking for 10 vehicles is provided with 2 service bays. An hourly parking rate applies for both day and overnight parking to the site (pay and display). Parking can be paid using cash or credit/debit card.
This site has an Aire de Service providing fresh water, charging for leisure batteries and a drain for grey water only. A dedicated sluice is provided for chemical toilets.

Whitehead -
There is sea front parking.

Park and Ride - click here to see the list of park and ride facilities.