Win the lottery and have it how you want it.
Seriously though if you are considering paying someone to restore a Defender then you need a LOT of money which you will never get back.
What would you like is the most important thing.
First thing I did with my son's Ninety was to clean all the fuse holder contacts and fit the correct rated fuses.
Can you disconnect the dodgy towbar electrics so you can discount that.
Swore at it when I realised the heater matrix has sprung a leak. Although the expansion bottle was empty it didn't take much to fill it up. Had just driven 120 miles in it so hoping all is OK!
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Any use?
Does it only do it when driving?
If you increase the engine speed while stationery does it make the noise.
You could remove the front propshaft and drive it, if the noise is gone then that could be you answer.