Weirdly bounce rate and exit rate have both increased. Traffic from yesterday is following the same trend as the day before in that typically page views are down 50% compared to before the changes were made.
This sounds like a textbook case of a redesign gone wrong - either misguided or poorly executed.
If bounce rate and exit rate are up and conversions are down, that suggests there are more issues than just borked SEO with the site.
I think it's not all that rare that a decent, well coded site with good SEO be taken down for some absolute rubbish because a marketing manager with no technical knowledge wanted a different colour scheme/look or similar and thought that required a whole new website from scratch. The lack of understanding many developers have of proper site migration procedures is also frequently appalling. I think a lot of people underestimate the impact this sort of work can have if poorly carried out, I'm sure such things are directly responsible for the failure of a number of businesses.
As Planet 13 says, I wouldn't trust a vague response like that from an IT manager. Have you tried looking to see if there are any pages from your old site indexed at web.archive.org?
Even if link structure, menus, page titles etc have remained the same, there could be issues with the back end setup of the site or anything in a whole array of technical issues.
There have been some changes but none of the URLs to the pages that were previously attracting a lot of traffic have changed
It's probably more to do with pages that have a lot of backlinks, which may not be the same pages. Also, any pages where the URL changes and there are not 301 redirects to the new equivalent will act to some extent like black holes for link benefit that is being distributed around your site.
I think this whole idea (which I've seen a few times) of trying to force extra conversions by sticking things like "get a quote" forms at the top of every page is usually misguided. Website usability/conversion optimisation is way, way more involved and subtle than most people give it credit for. It really is not as simple as "shove it in their face and we'll get more conversions". Such tactics are likely to cause visitors to consider you as pushy and cause a bad impression before they have even read a word about your product/service.
Also if keywords and links are so important WHY when I search for a certain search term do we appear 7th when some of the sites in the top 6 have: <snip>
Never be so sure about the data you are seeing! Also, seeing SEO as a kind of top trumps is massively oversimplifying things - there are according to Google over 200 ranking factors and these will interact with each other in very complicated ways, including some which are 'negative signals'.