Business broadband provider - rights?

Hi all! Very tricky pickle we've got with our broadband provider at the office, and I wonder if anyone can help/has experience of similar? I'm not going to name the provider at the mo - simply looking for advice on our rights and best way to resolve issue or get out of contract if possible.

We've had recurring problems with internet since it was installed in August 2018. The internet drops out for about 45 mins at a time, regularly every Monday morning, and also sporadically during the week. We're quite an internet-dependent business and it's cut out a number of times during sales webinars with clients, potentially costing £1,000s in business, given that the average purchase is £1,200 for our main product.

The facts of the matter thus far are as below:

1. Their sales rep came to the office in July, I explained our needs for internet provision, and she assured me the package would be fit for the purpose required.

2. The contract is business-to-business to we are seemingly not covered by the Consumer Rights Act, sadly. (Is this true? And is there any alternative provision?)

3. I first reported the dropping out problem on September 10th. They admitted their standard router wasn't fit for purpose, and suggested buying a more powerful, better router would resolve the problem, offering a small contribution towards that cost as a credit off the bill.

4. It didn't fix the issue, so I've continued to report it with three calls and two emails between 17th September and late November, as well as keeping a log of downtime. I mean, my home internet drops out from time to time, but not 2-3 times a week, for 45 minutes at a time. I can get a log of this to work out the exact times, but I estimate we've been on hold for about 4 hours of time on calls to them during this period. They have suggested every time to "power cycle" the router, which of course is always our first course of action, and haven't been able to do any more than that.

5. I called and tried to escalate the issue, eventually getting a response on 3rd December. They've sent an Openreach engineer out at their cost, after much debate about who should bear that cost, and he has found no problems with either the copper or broadband tests. That was much as expected, as we never had any issue with previous provider.

6. I am expecting a further call once they have these results to discuss next steps. Basically, though, it appears that the fault is on their end, rather than with our equipment.

7. There is a clause in the contract that states: "If the period of delay or non-performance continues for eight weeks, the party not affected may terminate this Contract on 30 days written notice to the affected party." Though the "party not affected" bit is quite ambiguous and suggests we don't have the right to terminate.

So that's the lie of the land. The ideal result for us is getting out of the contract on the grounds that the product isn't fit-for-purpose or as advertised, and that customer service has been poor and hasn't resolved our issue in nearly three months since first reported. All I'm seeking is some advice on what rights we have in this case, if anyone has experience of similar, and in the meantime I'll wait for the team to ring me back to see what they suggest on the back of the tests this morning.

Thanks so much in advance!

Jack