Scotland and Wales are countries, not ports. Do you know which ports you're visiting in each country, and how long you will have ashore? What time of year? Greenock (often described as Glasgow in the brochures) and Leith or Rosyth ("Edinburgh") are the most commonly visited ports in Scotland but some ships call much further north and / or at one or more islands.
We did a British Isles cruise in June 05.
For Dublin....Princess provided a shuttle (cost $4) to the Tourist Info Center near Trinity College.
Since there was five of us, we opted for a Taxi...avail as you leave the ship. Cost us $15 to Tourist Info Center. We got tickets for their hop on /off bus. It was perfect. We got on at the Trinity College stop...we enjoyed the guide...so we stayed on for the entire length. Got off at Trnity College & had lunch..Grafton street area. Then got back on the bus & went to the we wanted to visit. FYI...my husband loved a pint & we thought about going to the Guniness Brewery for their tour. Sice we were ow on time...we just stopeed for a photo & browsed their gift shoo & got back on the bus. The tour is not free & does take time. We were much happier spending our time & money in a pub enjoying a guniness
Wales....we docked at Holyhead. Very small town. Sweetest people we met. Has a beautiful church. The church's choir sand for the us. We popped into to bakery had some welsch cakes & tea. Kids got some trinkets from toy shops...all was happy. We didn't see any taxi...so if you want to go beyond Holyhead...you would have to get a car ot do a tour.
Greenock...we hired a guide & went to Loch Lomond & Luss
South Queensferry....took the train to Edinburgh...we were there on a Saturday & had a 45 min wait...in retrospect, we wished we had opted for a taxi. We took a taxi back to port. Did the hop on/off bus again