new discs due, other brakes i can use??

[riddett]

most properly quiete a common queston on here, mots due in like a few months, think the rear discs will be below spec.
just wondered if its worth me getting a new discs / caliper / pad set-up.
currently just running standard brakes all round. on a mk 1 vtr.

any direct fitting, cheapish, performance brake kits?
calipers from other vehicles?
green stuff pads?

basically while its due might as well upgrade it a bit.

thanks, jake