I simply do not understand one or two of the past few posts above, what is all that trying to achieve here, do the bare minimum to scrape through an MOT Test ???????????
Do the work correctly and avoid constant re visits of the same bodged faults !!
The OP Jody is taking the earlier and good advice from all on board and looking to do the job properly
At 17% there is clearly a problem with that Handbrake, as with all of them when they have not had recent maintenance. A badly adjusted one with decent Shoes will make 20% !!
My advice way back is given based upon what I see with MB's especially the pesky Parking Brakes on a daily basis, (they are all the same), also we have Salty Environment too being pretty much surrounded by Seawater Lochs.
Strip, Clean, Inspect, Check, Replace and Adjust as needed
The Single Seat Relay outputs 2 separate Feeds for the Left and Right Seats and develops dry Solder joints, which is what @M4rCu5
was eluding to.
Finally, I agree with @Mike6F
it doesn't strike me as odd at all that a decent Workshop would charge more for Quality Repairs with a decent Guarantee .............
Decent Workshops use Quality Parts and do a good thorough job, we don't quibble if a Customer phones and says there may be a problem, etc etc ..........
Therefore they have to charge more, I do, it is simple Business economics.
If you use the local "cable tie and insulating tape yee ha cowboy" to save a few sheckles expect to get your Car ruined, we all see these tales of woe here all the time, pay peanuts get monkeys !!
Cheap is never Cheap in the long run
HTH, Cheers Dave