In 8 days I would concentrate on either the whole time in Europe or stick in the UK.
Wales is fantastic, but a fair way from Edinburgh. Scottish roads are great and heaps to see so would fill 8 days no problem. There are also good bits between Scotland and Wales. 8 days would get you to Wales, have a day riding there and get you back, with time to ride and time to sightsee.
In August you will get about 18 hours of daylight in Scotland so you have heaps of time to ride.
Last June we did the following:
Channel tunnel to France, down middle to Millau and then across to Gap, north to Lugano in Switzerland and then continue to Frankfurt (not a good night) and continue to Assen for MotoGP arriving on the Friday. After MotoGP ride through Belgium and back on channel tunnel. That was 9 days, 2500 km and not a huge amount of time stopping to take it all in, which was fine by us. We had hired bikes in London for 4 weeks hence leaving from UK. We spent the previous week in UK with Wales and Mid England and had a ball with some great touring roads.
If you want a short spectacular blast in Europe look at OZAlps who I think do tours and rental in the southern alps which are fantastic. Check out Australian Road Rider as that has lots of ads for hire/tour companies including Europe. I think I have a back issue featuring this so will try and dig it out for you.
Avoid Paris, not that it is a bad place but not good traffic wise and it is half a day to get out to interesting riding areas (pretty flat around Paris and heaps of traffic).
In UK I hired from Raceways,
www.raceways.net, we got a mixed bag of bikes and it was sometimes hard to get hold of them. They are in London though. The 650's did the distance and were adequate, the 1250 did it easy but cost more and did not go much faster on the Autobahn.
Stick in UK or go Europe, either way it is great on a road bike. Depending on the week, check out WSBK and MotoGP dates to see if anything lines up, or the WEC or extreme enduro events.
Don't forget getting to the hire place, loading up and then returning can be 1/2 day each end so factor this into what you can do.
