I fitted a Britpart one earlier this year. In my defence, I didn't know I was getting a Britpart product when I bought it off Foundry 4x4. It took about 5 times longer to fit than my initial estimate. Par for the course. Instructions say drill holes through 2 rivets to make holes for the upper hinge bracket. I did this then found that the lower bracket fouled the lower door hinge, so I had to slot the upper holes by about a cm to get the upper and lower brackets spaced correctly. But.....I do have alternative replacement hinges by Gore [and beautiful pieces of art they are too], so standard ones may be ok. Or not.
The instructions show a black Defender, black wheel carrier.......printed in black and white. Absolutely effin useless. You'll find this out when it comes to trying to work out which way up the door plate is fitted.
There are 3 big washers and nothing to say where they go. I initially thought they were spacers for the swing hinges, use as required, and I did get one in to fit. Later I realised [guessed more like] that they go on the wheel mounting rods to stop the wheel from going too far on and hitting the door.
There's also a piece of tube with a strip attached to make a T. Again, jack s**t in the instructions as to what it's for and seemed to serve no purpose. Then I saw in one of Britannica Mike's YT videos on fitting one and he'd worked it out. I forget what it was, but it's not a fitted or needed part.
The sliding piston has a nut each side of its attachment bracket. You need to hold the nut fixed to the piston to stop it turning when you tighten up the outer securing nut. But it's difficult or impossible to access the inner nut with a spanner. I used a crows foot which I just managed to wiggle in.
Apart from these niggles, it's ok and functional now fitted.