I have now had to remove nails in two tires in the last month. If you have never done it, give it a try. It's amazingly simple. Much easier than running the car around to either fix the hole or get talked into a new tire. The TPWS is a real helper letting one know there is a problem. Of course, keep a spare also.
Plugging isn't the best method, but I prefer it. Prevents damage to my wheels, which is a major pet peeve. I've had good results with plugging, but had a few to leak.
In the UK/EU plugging tyres was outlawed many years ago although it used to be common. Now tyres have to be patched from the inside, or a mushroom patch fitted. and even then strict rule are in place as to how close to the sidewall a patched repair is allowed. The practice of fitting a tube into a tubeless tyre has also been stopped. About 8 years ago I had charity paper flag with a pin in it stick in the sidewall of a new tyre (one day old). Know one would repair it even though once the pin was removed the puncture could not be seen inside or out on the tyre and the puncture was very slow. I gave the inside wall of the tyre a liberal coating of puncture adhesive in the area of the puncture. The tyre never lost pressure after this treatment in 40,000 miles. John (Britprius)
Nowadays the plug material is very sticky so one no longer has to deal with the adhesive liquid, which was a bit messy. So that is a major improvement.
Plugging has not been outlawed in the UK, it has been classed as 'temporary' in the British Standard BSAU159 (in its various guises) which tyre repairers declare they follow as their minimum quality standard. Tyre sealants are also classed as 'temporary' as, like the plug, the repair does not include removing the tyre and inspecting the inside, which is part of the BS. Have a Google for "minor_repairs_to_passenger_car_and_light_van_tyres_31_may_2011.pdf" I am afraid the average tyre fitter has no knowledge of the BS and its details and so it is easier just to say 'it is illegal' Following BSAU159 the mainstream tyre repairers only do what are classed as 'minor' repairs. Anything classed at 'major' they won't touch as they really want to sell you a new tyre, plus a valve, (valves are reusable provided they are not ripped from the rim) plus balancing plus, plus. It is perfectly legal to repair your own tyre with a plug or indeed for any tyre repairer to do so, it just won't be to BSAU159.
Having checked out the UK regulations I agree in part with your post and stand corrected. This however is a minefield trying to decide whether EEA regulations over rule the BSAU and if you pop over to France the UK regulations are void. However BSAU159 states the tyre must be removed for internal inspection before repair, and any other repair must be considered temporary and not comply with BSAU159. Further your insurance could decline a claim cased by a non BSAU159 repair causing an accident because you declare on taking out insurance that your car will be kept in a roadworthy condition. BSAU159 also states any tyre rated V and over can only have one repair. John (Britprius)
If the hole is in the area between the treads- the modern plugs work particularly well and seem to last for the life of the tire. If the hole is in the actual tread area that contacts the road- the plug may fail. I had one in a tread area that failed (resulted in a slow leak) and on the second attempt to plug it I cut the plug off a mm or so below the tread surface to prevent it contacting the road surface. That repair has lasted more than two years now.
I always plugged my tyres when they were repaired - and they were repaired often. My local tyre dealer would only allow me to have one plug in one tyre though. Never had any problems with any of them.