I have an ex MOD 90 with a 2.5 N/A diesel engine in it. I towed a Brian James car trailer loaded with another 90 on it a few years back. It did it but it was the hardest bit of towing I'd ever done, I only went 40 miles but it felt like double. Your 110 might have a 1.6:1 ratio transfer box...
I had exactly the same issue, I put it down to a faulty relay socket as I swapped the relay and it still did it. I knew when I had a problem as the glow plug light never came on and the temperature gauge went straight to the red, even though it was cold.
It could be sucking in water through the air filter. Check the air filter box and there should be an outlet pipe with a valve on it to let water out, check this isn't blocked.
All Lightweights in service were fitted with 6.50x16 tyres but these are very hard to get hold of now. 205/80 R16 are similar size but not quite as tall and don't 'look right' A 750R16 tyre on a standard LWB (5.50Fx16) rim would be the easiest option.
...or insure it. Try getting a quote, as a second vehicle (access to a main vehicle) doing less than 1000 miles per year depending on your personal circumstances you could be looking at £75 pa or less. I used Confused.com for my classic quote and it was £58 fully comp with a £20 Halfords...
Have you bled the fuel system fully? Bleed at the top of the fuel filter then bleed the injection pump. Make sure your fuel solenoid on the injection pump is connected and is working, you should hear it click when operating.
It could be the voltage regulator in the alternator. You can buy new ones and swap the old one out, it all depends on how much f@rting around you want to do.
12V LUCAS ALTERNATOR VOLTAGE REGULATOR FOR- ACR 15,16,17,18 ALTERNATORS | eBay
I think you're right, the diff plug is the same, I'd need to get hold of one to check. I did have the part number somewhere but I'd still need the cradle so I was hoping that I could take an old leaky tank off someone's hands. The annoying thing is, I had one last year, sat around for ages...
Has anyone got an old series under seat fuel tank (civvy or military)? A rusty leaky one will do, I need the large drain plug and the cradle as they are missing on the one I have. I'm in the North West so anywhere nearby would be great.