Tricky one..... Key is understanding what will impact the warranty. I am sure it will come down to suitably skilled and experienced folk servicing it rather than it HAVING to be serviced at that specific garage. I would have a go at the...
Brake pipe is pennies but VERY fiddly to do, I would assume they need replacing on both sides, when my Defender had the same about 10 years ago it was £350 from a local garage to replace the lot.
Not sure on Prop shaft, if thats just a UJ it...
Should all be fine, you would have seen the temp rise surely, I had fan belt go in tunnels in Switzerland and couldn't see the temp as it was so dark and dash lights so sh1t, first I knew was radiator top blew which you should see steam coming...
If you are doing the job yourself it virtually never pays for itself to go stainless due to the price difference. You need to swap it something like 10 times to break even which is 30 odd years of use. However having said that that is based...