My mould is a basic tube 1.5m long x 300mm dia. So I have bolted the halves together to rub down the split. I have attached a picture of the inside. It shows the splits, and you can see how rough it is at points (this is the worst bit). Do I try to make the split better, or I am I worrying about nothing? I just don't like the roughness of it. If I leave it as is, I would imagine at worst it will mean buffing a bit of resin off the finished tube, which isn't a deal breaker. Any recommendations?.....
If I was to clean up the split lines, I would imagine the best way would be to get one half flat and apply release to it, then lightly chamfer the other half, then bolt them together, then smear gelcoat in to the join, then buff it down?

OK, so I have an answer to my own question.  I have tidied up the split lines. basically I rubbed down the gel coat to the flanges where it was proud of the flanges (think barrier weepage).  Then I did a trial fit, and voila, the gap is consistent, and straight.  There are still rough chipped corners at the split, but i have roughly filled these with Gelcoat.  I will let it cure for a few days then rub down to the flanges again, and so on.  Looking good so far.  I will try and post a pic of the final mould splits when done.

The reason this all came about is twofold.  Firstly I applied release agent at the wrong time - instead of applying it to the pattern as a whole, I applied it to the pattern after the barriers were set up, so it didn't really get right into the sharp corners.  Secondly, my barriers (polypropylene) should have been right up against the pattern (I didn't want them touching/rubbing against the pattern), but they weren't - a mistake, just get your barriers right up to the pattern. So i left a bit too much of a gap and filled the gap with putty. The putty was fine, but can move inward if you are stippling with a brush.  Next time I will spray.

Probably a bit much effort for what it's worth, you will always have a flash line that you need to clean up after. Having a tidy parting line in the mould makes it a touch easier, but unless the split line is 1mm thick then it is generally always easy. In any case, I am an advocate of putting all your effort into the mould, so it's not a waste of time. Just be aware that you will still have a flash line to clean up.