The guys at the MOT place should do it.
Depending on how big your rear tyre is, it varies along with make of tyre. For instance. My RS125 had a 150/70 z17 rear tyre. Cost me £110 Fitted & Balanced. & it was a Metzler (cheap) tyre.
Check your front tyre while your at it, as persoanlly I'd always replace them together but keep within your budget.
MOT = £30
Tyre = £80/£110
Fork Seal = £15 (Depending on where you get them from.)
The garage will give you a quote on all this to be fixed. Fork seals, if you feel upto stipping your forks then I can go through it with you, but if you'd rather let the mechainc take them apart then ok.
Close to £150/£180 for everything to be done, Best thing to do is do your own 'pre- MOT' checks.
Brake Pads
Brake Fluid
Play in F+R wheel
Play in Forks
All Electrics are working
Throttle cable springs back & isn't sticking (turn bars left twist the throttle it should snap back) Do the same for the right & back to centre.
Make sure the rear shock isn't soft (should be fairly hard to compress the rear end when stood next to the bike)
These are some of the basics I would check. Hope this helps.