Hello everyone!
I'm looking for info about Stuart mk III (M3A1) in British service during Normandy campaign and after.
Wich units used this version, where were mounted aerials of wireless set 19, fire extinguishers, aditional stowage boxes and other British equipment?

I'm sorry, but except in very specific circumstances, you're SOL.

By the summer of 1943, the Stuart III was out of primary service everywhere in the Commonwealth armies in Europe. None of the units carried a Stuart III on their normal war establishment. That said, some units still had them in unusual jobs. There is a photo of at least one old M3A1 hack in an infantry unit ( I think) and there's another photo of a turretless Stuart III as a unit commander's runabout for a Canadian Brigade HQ. I would also bet that several arty units had them as FOO's chargers, but I haven't seen such a photo.

But, unless you can find a specific photo that has a unit identified against it, you really can't build an accurate NW Europe Stuart III.

Sorry to be the bearer of bad news.

If you do find a photo the radio will be at least a No 19 set and possibly a No 38 infantry set. The No 19 set will be in the right hand sponson with the main antenna ("A") in the normal US radio spot (engine deck over the air inlet) and the second, "B", arial on the right side, behind & to the right of the turret ring. A No.38 set arial may be attached to the vehicle or may just be extended up through the hatch.

As for specific Brit fittings, take a look at photos of Brit Stuarts from the North African desert war period. Most of those fittings would be appropriate except the sand shields, but, havingbeen in service for more than 2 years and being out of their main line of service, these thigns could have been fitted with almost any kind of fitting that would suit its new purpose. Photos are your key, here. The two photos I know of have the Stuarts so overloaded with stowage & kit that it's actually hard to tell what kind of vehicle is under the "gypsy caravan" pile of crap.

HTH

Paul