Sounds like the problem is going to be a thing of the past tomorrow then!
You can replace the seal yourself, it is only there to keep dust out and the MOT men very rarely fail a care if it is ripped, they test the brakes so they know it is working efficiently anyway.
It is a little tricky to replace though, or should I say fiddly.
Nothing that can not be achieved with a little patience. You will need to take the said calliper off with the brake line attached and then press the brakes fully around 3 to 4 times to let the piston pop out. It will be best to have some one handy to hold it and tell you when to stop.
Once the piston is out you can pull the seal off and replace it which is the tricky part.
Next, you will need to push the piston back in making sure it is level all the time, this is the fiddly part.
Give them a refurb buddy, it will improve the looks and efficiency of the components which makes it worth while for sure.
You may want to upgrade the brake hoses at this point too.
Keep us posted on how you get on buddy.
El