Of all the news about high loan-to-value (LTV) lending this week, it's the Nationwide news that's most interesting.
https://www.nationwidemediacentre.co.uk/news/nationwide-helps-generation-rent-become-generation-buy-as-society-increases-max-loan-to-income-ratio-for-first-time-buyers
Nationwide, like last time, aren't using the government's Mortgage Guarantee scheme but the message it sends to lenders is useful for them.

Side note: the guarantee scheme should help improve the availability of higher LTV mortgages but it's only really fixing the impact of the pandemic (the decline in the last few bars on the chart below) rather than the longer term issues of high house prices and tighter regulation

The reason the Nationwide news is interesting is that they appear to be taking advantage of something that we've been aware of for a while but none of the major lenders have been willing to do until now and it's around what stress test rate is applied.

As I noted in Oct ( https://builtplace.com/digging-deeper-high-loan-to-value-mortgage-lending/), in theory you can be stress tested on the rate you will be on after 5 years. So, if you have a 5yr+ fixed rate, it could just be that rate. But, until now, & due to conduct risk, lenders have typically still tested at the higher rate

The conduct risk here is lenders could be seen to be forcing borrowers to pay more on longer term fixed rate periods in order to borrow more.
It now looks like Nationwide have satisfied themselves and the regulators that they can do this appropriately.

So my reading of the release (& do correct me), is that Nationwide will be stress testing you on your actual rate if you have a five year or longer fixed rate period.
In cases where the stress test was the constraint, this could enable more people to afford the home they want.

This could be inflationary but the £1billion probably only translates into 4-5,000 mortgages and the soft cap on lenders lending above 4.5x income will limit supply.

It also doesn't help if the deposit is the constraint as, if you're up at the 90% LTV limit, you'll need a 20% bigger deposit if you want to borrow 20% more.

So this approach, if taken up by the wider market, reduces the constraint of stress testing on SVR+ and probably does more to deliver on the government's promise to turn generation rent into generation buy than anything from government so far.

Though it's possibly only a one-off to the current generation of first-time buyers with future generations faced with higher house prices and needing bigger deposits.