It’s always been very difficult for anyone to compete with Motability, as it’s only Motability that has the block VAT exemption. That situation remains (at least for the core lease), so they retain that competitive advantage.
However, if Motability persist with the 25p per mile surcharge, which would add £7,500 to the £13,000 sacrificed benefits plus AP (for someone who does 20,000 miles a year), then a private lease, where you can set your annual mileage up front for a fraction of the cost that Motability will now charge, may start to work out a lot cheaper, even with the VAT included!