The only countries in Europe that allow more than 80km/h on motorways when towing are:
Austria (100km/h if the gross train weight does not exceed 3.5 tonnes)
Belgium (120km/h)
Bulgaria (100km/h)
Cyprus (100km/h)
France (130km/h for outfits under a max. permissible gross train weight of 3.5 tonnes, otherwise 90km/h)
Germany (100km/h, if certain conditions are fulfilled)
Luxembourg (90km/h)
Netherlands (90km/h)
Portugal (100km/h)
Romania (100km/h)
Russia (90km/h)
Slovakia (90km/h)
and, of course, the UK
Austria (100km/h if the gross train weight does not exceed 3.5 tonnes)
Belgium (120km/h)
Bulgaria (100km/h)
Cyprus (100km/h)
France (130km/h for outfits under a max. permissible gross train weight of 3.5 tonnes, otherwise 90km/h)
Germany (100km/h, if certain conditions are fulfilled)
Luxembourg (90km/h)
Netherlands (90km/h)
Portugal (100km/h)
Romania (100km/h)
Russia (90km/h)
Slovakia (90km/h)
and, of course, the UK