Grass seed for heavy ground

Something with an even mix of tetraploid and diploid. Agritech No 4A is a fairly good mix I find

I Second Agritech 4A, have used it on similar type ground, very happy with it.

I didn't plough it though, I'd be afraid id turn up too much Marle.

Don't think that would be suitable for the type of ground the OP is talking about. Those mixes would grow too much in the shoulders when grazing would be difficult on heavy ground. Those grass varieties won't survive without proper grazing and nutrients. I'm not sure what the right type of grass seed would be though, how about some type of meadow grass with more summer growth?

Well that type of ground is common in the midlands and its what is mostly sown around these parts

Including my own ground

Yep - Fescues good too and Marsh Foxtail, all deep rooting and resistant to waterlogging

Cocksfoot, Timothy and meadow fescue should probably make up 60-70% of the mix. Ryegrass for the rest, unless you were going to do a big drainage job and horse out the fert.

what method do you find best? Disc?

But definitely not cocksfoot, I hate that old variety

I'm a great believer in ploughing. If it's an old field ploughing will loosen up the ground and you'll have 6-8" of ground that will soak water better. I had a field here last Yr that hadn't been ploughed in almost 50yrs. Very wet in places. Ploughed up the pan only had about 4"of sod in places grey white clay and stones. I had visions of it being a total disaster. We took a chance growing fodder beet on it and it grew a fine crop. Ploughed it up again and Reseeded it late April and its growing grass fine. Will be cut for bales for while.

Yeah the man on the plough this spring went down as deep as the man last year. You'd see the rotten sod coming up again. I was advised to roll it with a Cambridge type roller as opposed to a smooth roller as if it got wet and dried again it'd go like concrete.

My own thinking is the marl/hard white pan holds the water and slows the leaching of nutrients hence the great response . A run of a subsoiler or mole plough would probably of benefit as well.

Soil test first. Your soil could be goosed from the 7 years

Drummond do a mix for difficult soils

Once you plough shallow you should be OK. If it's well rotten then it wouldn't interfere with a disc harrow either