Okay, scrap that. Went out 2 hours later to a small puddle that smelled of fuel. But i now have a theory! Since i reconnected the fuel return, the pressure in the fuel system is going to be different. Is it possible that pressure and heat built up while driving, even short trips, causes the fuel in the tank, (a hair shy of halfway full now,) to expand or move around in the tank, and end coming out of the breather outlet on the filler neck? Would mean the hose at that end isn't on properly. 

Will be whipping that inside rear panel off tomorrow to check what i can and adjust if needed.

I've taken that panel off, the pipework behind has fuel on it at the filler neck end but is dry everywhere else. 

Taken rear wheel off, only evidence i can see of a leak is the larger breather hose. The hose is attached but is at an awkward angle so the filler neck breather outlet is not lined up correctly with the pipework that runs inside the shell for the breather hose to go through. 

Is it possible for just an incorrectly fitted breather hose to leak as much as it has? Probly had around 2 litres come out in total so far. No sign of any other leak on the tank. 

The larger breather pipe is inside a tunnel in that space.

I could not pull the old breather tube out, I think combination of rust in there and that it had become very hard

 

I ran a new tube in parallel and used a Herbie clip to attach it to filler neck.

Inside the wheel arch, i only see one hole for the large breather to go through. I'm guessing that is the solid pipe that runs through the side panel. Did you have to drill another hole or were you able to just connect it up? 

As far as i know, the pipe is fine on mine. Looks and feels okay to me. No rust i can make out. Can't actually see the filler neck end but it feels smooth, consistent with the rest of the pipe that i can actually see.

I'm hoping to get some time real soon to get the tank off again so i can check that. I have already drained it as it was leaking out anyway.

In very hot weather with nearly full tank yes a lot can escape while stationery if vapour does not go up the upside down U trap.

 

I made another hole which was easy as the outlet was quite rusty.

 

Smothered it in underseal after waxoyling inside. Probably should have cleaned up more. 

Okay.

Mine was half way full or just under so i could be looking for another leak. 

I think the pipe on the car is okay, just doesn't line up with breather outlet on filler neck. It's the correct height, just a few degrees out on the angle. May try and bend the filler neck outlet just a little if i can. 

Thank you.

Checked it all over. Can't find any signs of a leak on the tank, that is solid. 

I think, i may have missed the outlet on top of the gauge sender end of the breather and overtightened the clamp. Think that caused a build up at the filler neck end of the breather, and that caused the leak on the old, tired pipe. I've changed for a new, snug fitting pipe and all seems good so far.

Yesterday, adjusted the clamp so it isn't crushing the pipe any more. Went fine driving today. Filled up to just shy of full tank. Still had slight fuel smell but not as bad as before. No sign of leaks though. 

Nice.

Well i cheated a little bit. Had a bbq the other night, invited a couple mates, (in my social bubble,) when they rocked up, the car was already jacked up, rear wheel off. They asked what was going on, told them, an hour later, we had dropped the tank, (again!) Replaced the breather hose and put it all back together. They got food and beer so they didn't mind. 

There was a really small nick, probly around 1cm, maybe a little less in the hose where it goes into the wheel arch/body at the filler neck end. I think it's the hose it had from the factory so not a bad run. 

All connected up correctly, nice and snug, double checked, running great, no fuel smell any more. Even taken for a run to confirm. 

Thanks for your help and patience dudes. Very much appteciated. Keep safe.