Never found it necessary to clamp brake hoses and loosen the bleed nipple before pushing (or screwing) the brake pistons back in and never had a problem.

In fact on the Caterham this would not be possible since the braided brake hoses would be impossible to clamp and would probably be damaged by doing that. And its not just Caterham that fit braided hoses.

As for the level of fluid in the master cylinder rising i simply remove the lid and using a syringe remove a little when the fluid rises.

In any case, why would you want to push old, degraded, possibly dirty and wet (water content) fluid back up into the system?

The fluid in your calipers should be no older, more degraded, dirtier or have a higher water content than the brake fluid elsewhere in the system.

If you suspect the fluid is in that condition the system needs bleeding.

Err the fluid in calipers ios usually balck with dirt from the pistons and bits of rubber from the seals... And water gets into teh fluid either from teh filler cap or from around the seals...

Precisely so bleed to whole system rather than just bleeding a little out when you push the psitons pack with the nipples open.

But if water is getting in around the seals the calipers need refurbishing. If the seals are falling apart the calipers need refurbishing.

Probably the last time I'll be doing my son's Fiesta because I think he plans to sell it shortly. I'll be selling my 2007 Focus in January and buying nearly new Fiesta with low miles (hopefully), so might not be working on brakes again for some considerable time.

However, its still been a fascinating discussion which no doubt applies in principle to all popular cars, and thanks to all.

Just one other point: I note the advice about "working" the bleed screws one way then the other, after applying copper ease to make them easier to remove. Is it feasible (or indeed advisable) to remove them completely, clean the threads up with a wire brush then put them back?

Yes if you clamp the hoses or all the fluid will drain out. You also need to take EXTREME care to prevent rust, oil or grease from entering the open hole when the nipple was. So clean around the outside first with great care.. and plug the hole with clean thick paper towel (Scott's blue is ideal)..

Personally I never do: just uncrew a few turns and use a copper wire brush to clean up the threads which are visible. Far less risk of dirt entry.

I've done this myself. As Mad says, make sure the area around the nipple is scrupilously clean before complete removal. I usually wire brush, followed by plenty of brake cleaner. I use a small screw to plug the hole usually without clamping the pipe - any fluid flow out of the caliper should prevent any dirt going the other way.