I'm not, but I have read some stuff about the problem with austerity as an approach.
But they haven't spent more and more on infrastructure. They have cut expenditure repeatedly to service debt. The last "spendy" Government was the Blair / Brown era. In 15 years things haven't got better. To me, this suggests that the austerity approach isn't working.
I am not an economist either, but, I think I am beginning to understand, it is a bit like leaves on the line, or, snow on the line, borrowing to spend is fine, as long as it is the right kind of spending.
In my simple, non-economist head, one of the problems is that the consequences often lag way behind the actions, so, no-one (especially the economists and the politicians) ever learns what the consequences of the proposals and/or actions are.
But, I trust I am wrong, borrow more and more, build "infrastructure" everywhere, sounds fairly straight forward to me, although, if it is so simple, why isn't everyone doing it?