Just an update
Looked at the keyboard cases but none of them seemed to offer me what I wanted, so I eventually made contact with Steve Clarke and ordered a Rifle case 1807A
I ordered it over a weekend and it was sent out Monday, arriving Tuesday.
It's very nearly what I want and with a few easy modifications I've been able to make it just about perfect for me.
First off, it stands up on it's own (so long as you don't have anything too heavy in the massive side pocket.
It has 4 bits of foam in it (2 on each side) which aren't glued in, but that's what I wanted - If it gets wet I want to be able to dry it out by removing the foam so that's fine. You could glue it in if you wanted to but I don't.
There are straps inside the case to keep the gun in place during transit, but I don't need them 99% of the time so I've just tucked them behind the foam. There's also a stiff bit of nylon covered foam about 3 inches wide under the zip to give it some more rigidity, but that just gets in the way when I'm getting the rifle in and out of the case on a course, so I've cut that bit out on the top part, leaving the sides in place.
There's also no foam in the base of the case, so I ordered a piece of foam that was 45" x 7" x 3" at a cost of £12 delivered. It was too big - I could have got away with 45x4x3 but it's easy to cut with a bread knife (or an electric carving knife is perfect if you've got one and the other half doesn't catch you using it).
So I've cut that to fit in the bottom of the case with a slope in it so the rifle sits level.
And that's it - spot on. I can stand it up and rest it on the floor next to me on a lane and just lift the rifle out without the case falling over.
If you need any custom grey packing foam cut to size, I found these to be pretty good
It says on their website that they only supply to Trade, but they were happen enough to cut some foam to size for me.