Unfortunately, the TDC didn't have any seal kits in stock so I ended up getting one on ebay. It came in the post yesterday and I fitted it without any problems. Once the brakes were bled they were working once again.
The subframe mount will need to be sorted out. This means that the engine will have to come out. If I had an engine crane this would make it possible to do the job. I'm also considering replacing the subframe bushes at the same time.