St Asaph, one of the smallest cities in Britain, is in Denbighshire as are the towns of Denbigh, Ruthin and Llangollen.

Denbighshire County Council

There is nothing on the website concerning motorhomes. Most car parks have height restrictions of 2.1 metres but a search for motorhomes brings up a list of car parks that are open 24 hours a day. Not sure what this means.

The car parks below all have a capacity of over 100 spaces so if a MH can get in there may be a bay available.
Corwen - Green Lane LL21 0DN - 111 spaces no height information.
Denbigh - Barkers Well Lane LL16 3TS - 186 spaces.
Llangollen - Market Street LL20 8RB - 147 spaces.
Llangollen - Horseshoe Pass. Ponderosa Cafe. Lareg car park. Bikers use it at weekend. HF.
Llangollen - Horseshoe Pass. Laybe to pull over and look at amazing views. HF.
Prestatyn - Barkby Beach LL19 7LG - 215 spaces.
Prestatyn - Nant Hall Road ll19 7LE - 123 spaces.
Prestatyn - Nova Central LL19 9AA - 108 spaces.
Prestatyn - Nova West LL19 7LP - 624 spaces.
Rhyl - East Parade LL18 3SG - 331 spaces.
Rhyl - Marine Lake LL18 1LN - 175 spaces. Free.
Rhyl - Morley Road LL18 3HG - 227 spaces.
Rhyl - Quay Street LL18 1UN - 204 spaces. Free.
Rhyl - Rhyl Pavilion LL18 3AQ - 244 spaces.
Rhyl - Sky Tower LL18 1HF - 158 spaces.
Rhyl - West Kinmel Street LL18 1DA - 190 spaces.