I thought Bluestone 42 was a bit poor to be honest, the humour was fairly childish and it had a very predictable script. More akin to a student film rather than a professional BBC production. But as far as inaccuracies in technical details and equipment go, that sort of thing may bother those who think that everything in the text books is how it actually is in reality, but it very rarely is, especially when abroad where supply logistics can often be a problem. And as others have pointed out, it's meant to be entertainment, not a documentary, so I think we can let some technical detail inaccuracies slide too.
In any case, there are loads of examples of people using non-standard issue gear or modifying equipment in the field during times of war: Battle of Britain pilots painting their Mae Wests with yellow dope so they'd stand out if they bailed out into the Channel. M113 APC crews putting flak jackets on the floor of their vehicles to increase the armour, and knocking up steering handle extensions so they could sit on the roof to drive and avoid being killed if a track went over a mine. Soldiers in Afghan and Iraq buying their own boots and wearing keffiyahs (before they were issued). Vietnam war door gunners spot welding an empty rations peach can onto the side of their M60s to make the rounds feed into the breech better. M79 Blooper gunners removing the front sight from the weapon so it didn't catch on bushes and aiming by guessing the tilt angle instead. F86 Saber pilots in Korea removing the lead computing optical sight from their aircraft and replacing it with a piece of well chewed gum stuck in the middle of the windscreen. Soldiers in tropical and dusty climates dropping their M16A1s and using AK47s instead the moment they could get their hands on one. Kriegsmarine Uboat crews in WW2 wearing British Army Battledress tops from captured stockpiles in France. Huey crews in Vietnam painting their (white) issued helmets green. Israeli pilots flying Avia S99 (Messerschmitt bf109s) fighters in the war against Egypt. Egypt using the C47 transport aircraft as a bomber against Israel. Red cross and Red Crescent medevac vehicles mounting guns, despite this being against the Geneva Conventions etc, etc, and I'm sure you can all think of many more examples.
Non-standard stuff and modified equipment is really quite common on the front line, so unless an anomaly in a movie or TV show isn't blatantly stupid, patently impossible or obviously anachronistic, then we can't really say it is inaccurate.