Route help.. well, there are websites for tourers and such, but to be honest you might as well just look at a map. I presume you’re starting from Cardiff, going by your username? You could make a loop of it for not much more distance I reckon. Cardiff to London, then Edinburgh, across to Belfast (Glasgow is it?) then Dublin, ferry back to Wales via Holyhead.
Use bing.com/maps for unlimited online OS maps. I can’t recommend much personally, but getting to London should be ok, from Bristol eastwards is lovely rolling countryside all the way to Reading. You could opt for NCN route 4 which goes from London to near Cardiff. Not sure about getting to Edinburgh though, but you could try this.