I have just got a zvezda T80bv kit as a cristmass present and wonderd what upgreads i could do to the kit and what aftermarket kits are avalable for it? Can anyone help?

Zvezda re-packages old DML molds, so anything that is labeled supposed to be a fix for DML kit also is fine for Zvezda.
main gun barrel:
Barrel Depot makes decent 2A46M barrel
Model Point makes spot on accurate 2A46M barrel in two versions: with and without thermal jackets
Machine Guns:
As far As I know only Model Point makes hollow barrels for both PKT 7.62 coax. and NSVT 12.7 machine guns
Suspension:
SP Designs have very well detailed road wheels, there is also a good track set from them
MasterClub offers road wheel set along with their individually pinned tracks set
Miniarm also makes T-80 tracks plus specific idlers and sprockets to make T-90 out of Tamiya T-72M but you can use tracks only for T-80
Modelfixer makes accurate plastic tracks that can be assembled working or fixed. They do not fully show fine detail on guide horns because of technology limitations, Long run plastic vs pressure cast resin, but if you are on tight budget they are certainly good candidate to consider.
PE:
Eduard has very good PE set that will enhance overall look of otherwise crudely done stowage bins and fine details.

Nonetheless, all that still won't let you build accurate model of the tank. One of the biggest obstacles is the turret which is nowhere near what actual T-80B turret should look like in 35th scale. There is no conversions of any kind on the market today. Theoretically, you can buy Miniarm T-64B turret without neutron absorbing applique and adjust it, contrary of popular belief they are not the same, according to drawings and photos, but it will cost you good deal of time and money. There are also discrepancies in hull dimensions and just about every other large detail, skirts, sights, front hull, engine deck, etc. Some of these are relatively easy to fix with sheet styrene, engine deck along with exhaust, however, present the biggest problem due to complex detail or lack of such in DML molding. SP Designs makes corrected engine deck but it comes in comprehensive conversion set for T-80 U. Finally what really makes this tank stand out, Kontakt-1/3 ERA, is the least accurate part of the kit. Your only options are to either wait or try finding good, but hard to obtain Model Point sets, type A, B and C.

I see what you mean i am having some issues with the fit of some parts!!