Nigel - Well that certainly sounds like a challenge!
I am sure if you start any work, even a small job, the encouragement from the forum will help you build up from there and keep going.
I put off a lot of jobs on my own build based on fear and most have turned out OK (ish).
Obviously many jobs have taken miles longer than I expected / hoped, but if you don't start, you'll never finish.
I've also found that seeing other builders tackling their "issues" gives me more confidence to tackle mine.
Good luck, Paul.
PS
Remind me where your farm shed / workshop is?