You would think the Mini suppliers would sell them, especially the rears which seem to crap out on a regular basis.

My experience with wheel cylinders is that they don't "wear out".. rather the interior of the cylinder corrodes due to contaminated fluid.  The rough edges of the resulting pits in the cylinder wall then allow fluid to leak past the seals - or chew up the seal itself.

The solution is stainless sleeves in the cylinder and good quality seals.  The local shop does this for about the same $$ as new cylinders whcih provides a pretty much lifetime solution...

Cheers. Ian

 A Very small stone Hone is the right tool to ' clean up the inside of the bore.... 

but in a pinch ive done  a few cyl rebuilds with very light wet dry sandpaper - wet with brake clean   Rolled in a tube to clean out the bore too ... passes thru - clean out the gunk or any spots  shoudl go back together good as new.

Goodluck

thanks guys! the truth is i found just the seals at my local brake store for 3$ a piece, whilst complete cylinders for 20$. Will take them apart and see what i got, hopefully i wont have to replace cylinders!

There is conflicting information about the reason for failure.... It seems less than 5 years in a garage should NOT 'wear out' new wheel cylinders!  Some say 'new' brake fluid is destroying rubber parts while others say the rubber parts are now inferior.... It would be interesting to dig into some premature failures to see if there might be a pattern.

As to the choice of new vs rebuilding, I tell people to pull them apart and LOOK at the condition of the bore BEFORE deciding, and also that most of the wheel cylinders don't cost that much more than the kits, so how much fun is it?

I had a 5/8" rear cylinder (Brake Equipment brand, Italian) leak after 18 months, a couple of years ago; it has been fine since I put a seal kit in it.
If the bores of yours are not pitted, I'd just fit new seals.

I've replaced the wheel cylinders all around back in 2010 (drum car). Since then the car hasn't cover more than 2000 miles and was mostly garaged! Recently i've noticed the car pull side. I had changed all hoses about a month ago! I also found  a line connector leaking so i thought this might be it! Fixed that as well and it kept pulling! Today i went inner depth and pulled the drums out! i've got three busted cylinders at front! I haven't tried to repair cylinders so far. Just wanted to ask if anybody has gone this route and has any experience with the repair kits and if they last long, do they worth it? or should i go straight to new cylinders.

thanks in advance