Anglesey to Newtownards is only about 75nm; do you really need to stop for a top up that close to your destination? Also, I'm not sure that either Valley or Mona would be in a position to give you fuel.
The route most follow from the south is via Welshpool, LYNAS (NE of Anglesey) and RINGA allowing you to cross the sea clear of CAS at FL65 with about 65nm over the water. If you need to stop, Welshpool or Sleap are good options, leaving about 150nm to Newtownards
If you're not happy crossing the mountains, head up past Sleap towards Hawarden and then coast out at Point of Ayr. Two options here: direct via IOM (this adds about 30nm to your sea crossing) or along the North coast of Wales towards LYNAS.
ATC (at weekends) would be London INFO (124.275?), Ronaldsway Radar (120.850) for transit through the IOM CTR/CTA and Belfast Radar (130.850) before changing to Newtownards. Weekdays - Shawbury/Valley will be useful.