So first of all the word "Mercenary" is always a great sell for viewing/reading numbers.
3,000 Brit volunteers fighting in Ukraine, not a chance, several hundred at the most, all in the Ukrainian military in some shape or form.
As for UKSF or other SF operating in Ukraine, who do you think does the close protection for the diplomats in Kyiv or visiting dignitaries? The SF chaps.
No doubt some are also involved in planning of certain Ukrainian SF missions. UK PLC can not afford to have dead serving SF chaps coming back from Ukraine, the Russians would have a field day with the propaganda.
3 ex SAS were killed in Lviv in the early days of the war when the base was hit, the number of dead was around 280 not the figures given in the press.
Wagner group are what the West lump all Russian contract companies as, but Alpha group is one of the main players:
As for France v Russia in the CAR what a load of dribble.