[bkulcsar]

Thanks for all the replies.
I will definitely change brake fluid as well. It was changed more than 2 years ago. Nipples are OK, I sprayed them with WD40 a couple of days ago and today managed to break them loose.

So far ordered caliper repair kits. Received them today. They are complete kits along with the bleeding nipples and pistons. Unfortunately the rear ones do not fit, they are 39 mm diameter and I need 42 mm. Front ones are 60 mm and they seem to fit. Will return the rear ones on Monday. Luckily I ordered them from a local shop (despite being more expensive than online shops), so turnaround time won't be long.

Examined the brakes today and noticed that the rear break hoses have tiny cracks. Decided to put 4 brake hoses (Ate) on my shopping list. The fronts are OK for the time being, but if the rears are beginning to develop cracks... the front ones won't have too much life in them.
Rear break discs and pads are not worn, decided to let them be, just rebuild the rear calipers and replace the brake hoses.
Front ones are not worn either, but they provide a great deal of judder, so they REQUIRE replacement. Disks, pads, hoses, caliper rebuild kits and fluid.
Since I won't replace the rear ones I decided to go for Ate (for all parts except rebuild kits). Pagid is hard to source in my country (must be ordered from abroad which takes time) and time is ticking. I will need to replace the brake servo seal as well (ordered and received the replacement polyurethane red seal from eBay).
I will let you know it went.