lol i had an Allegro and it was the least rusty car ive owned, no these cars had the worst built engine and drive system in the world ever.
You had the A series engine up to 1.3 and then you got the Maxi engine from 1.5 to 1.7.
The mini engine could not haul the weight around and broke gearboxes and shafts like butter, even more so when you run the hydrospastic suspension low to look cool

or if it just leaked out overnight on your drive.
The E series engine was just as pants, they did go up to a 2.2 straight 6 which was muchos pantos as well.
You could however fit any "upspec" BMC parts with little bother like four pots, MG wheels, Turbo engines etc etc, but these were made of cheese too.
My leggy had twin headlamps, chin spoiler, Princess brakes, MG wheels, slammed on its arse either through stupidity or a leaking "shock" and all the power you could get from a 1275 A series without blowing the head on a steep hill

(very difficult car to push due to the shape of the rear)
I was getting 13mpg from it so sold it for a 240GLT Auto which got about 25mpg and was cheaper to insure.
I had fun in my leggy but it was in no way as good a Mk2 or even a ford fiesta.
I do think the Mk1 is the best out of the bunch so far as original concept and design, with the low point being the Mk4. But even the worst golf is a streets ahead of any "British" cars they competed with