OK, as I live in the UK, I'll start with that. I'll also try to add my personal opinion of the "driving" conditions, as well as the general opinion of the various places.
UK - Scotland: (most places, including Shetlands and Western Isles, but not Orkneys, nor some of the smaller islands). Driving roads are generally excellent, and the Scots are undoubtedly the best of the UK drivers. I don't think Scotland needs any general explanations.
UK - Northern Ireland: (mainly the western areas of the province [well, actually all over the province, but I was only about 3years old!!!], including Derry, Strabane & Enniskillern). Good driving roads, good countryside, and generally friendly people.
Republic of Ireland: All over really, appart from a few of the central inland towns. The roads range from OK, to truely shocking - and avoid the "Ring of Kerry" as the numerous tour busses never give way, and straddle the white centre lines without a care in the world. Generally, the people are extremely friendly, with one blatant and scary exception of County Clare (wierd scary spooky interbreds!).
UK - Wales: All over (I can't think of a single town I havn't visited). There are some great driving roads, and the pricipality is generally a very picturesque place. The "locals" in some areas can sometimes be very rude and unhelpful to the "English", and also to any other outsiders.
UK - England: I've been to most areas in England, though with a couple of noteable exceptions (Surrey, some parts of Lincolnshire, and some areas of Lincolnshire, & IoW). Some of my fave areas (in no particular order of preference) - Northumbria (great scenery and driving roads), Lake District, Yorkshire, Leicestershire, Suffolk, Herefordshire, Worcestershire, Devon, Somerset, Dorset, Gloucestershire, Wiltshire & Hampshire. Areas to avoid: Cornwall (some lovely quaint scenery, but roads are shyte, and seem to be permanently gridlocked).
Denmark: Around the Esbjerg and Arhus/Randers areas. Lovely country, good beer, OK roads, and extremely friendly people (particularly the women

). Would definately like to see more of Denmark, and particularly Copenhagen.
Netherlands: All over really. I particularly liked the Drenthe, and along the coast. Roads generally good to excellent, though driving in central Amsterdam was not particularly pleasurable. The Dutch are an extremely friendly bunch!
Belgium: Not spent too much time here. Mainly Brugges (didn't do anything for me) and Brussels (OK). The roads seem to be quite good, with reasonably proficient and well-behaved drivers.
France: Basically all the north and west coastal areas (the channel and atlantic). Some of Pas de Calais (the channel ports, particularly Dunkerque really are aweful, but Amiens is nice, as is Fourmies), all of Normandy (Rouen v.nice), Brittany (Brest is best

) and Loire (Le-Mans needs no further explanation, suffice to say that you can go flat-out on the public part of the circuit, and St Nazaire is interesting). All of Poitou-Charentes (Angouleme, Poitiers and Rochefort are all particularly nice). Some of Limousin. Nearly all of Aquitane (Biarritz was a huge disapointment, but Bordeau and the Landes forests were nice). All of Midi-Pyreneese (all stunningly gorgeous, with Pau being exceptionally stunning), and Languedoc-Roussillon (Carcassonne deserves an exceptional mention, as does Millau for the bridge, and the now quaint town. Montpellier was a nightmare, and gave up in the end). Also the northern fringes of Champagne, Lorraine and Alsace (Nancy was beatiful, and Strasbourg was a sh!t-hole). Never been to the Rhone-Alps, nor the Provence/Cote D'Azure areas, so they are on my "must do" list. The french roads are generally excellent, as are the drivers.
Andorra: Just like a morph of southern France and nothern Spain. Good duty free shopping. Some roads OK, some shyte. Plenty of tower cranes.
Spain: to add
Germany: to add
Austria: to add
Switzerland: to add
Italy: to add
Sardinia: to add
Morocco: to add