The UK doesn't have a law prohibiting filtering but lane splitting normally results in a "riding without due care and attention" summons. There is no proscribed upper speed limit or method of filtering in the Highway Code (the rules of the road) but, if you are travelling at more than 20 - 25 mph or weaving between lanes, expect a "without due care and attention" or dangerous riding summons. About 50 years ago, for a very short period of time, an upper limit of 27 mph for filtering was mentioned in the Highway Code.
In France there is a specific law covering lane splitting but there seems to be no law covering filtering. The law for lane splitting only allows it on Autoroutes or dual carriageways at speeds of under 50 km/h (31 mph) under very specific circumstances but, there are caveats! There are signs on some major Autoroutes advising motorists that lane splitting is legal. Motos (motorcycles and scooters) filtering to the front at junctions is the norm but there is no law allowing it - in France, in general, you need a law to allow you to do something, if there is no law, it is usually prohibited.