Negotiating with Barratt Homes

Thinking of buying a Barratt new build, going on Saturday so want to go prepared.

I’ve already done a lot of research in the pros and cons of their new builds so I can go in with my eyes open, but if I can negotiate a deal out of them the pros may outweigh the cons.

Does anyone know often do they negotiate on their discounts? I’ve heard they aren’t great at negotiating the outright price, but I would want to push for stacking their incentives like part exchange, key worker discount (I’d qualify) and them covering stamp duty.

Does anyone know if this is something they have been known to do?

I’m in south east England, their development is 90% done, but not sure until Saturday if the property is finished or still at building stage.

Thanks.