So much of this depends on what's available in your area, whether you can get FTTP, and if it's FTTC how far you are from the cabinet/junction box.
We get on OK with Virgin, and it's pretty much our only option. But we're also in an area that was entirely cabled by Telewest back in the day, so the infrastructure is all there underneath.
You might be better asking more locally for recommendations specific to your area. We got on OK with Hyperoptic at our last address, but they don't supply to our current one so we've had to go with Virgin.
The people I know who can get Zen usually say that the broadband speeds are stable and reliable, the customer service is good, and that any issues are sorted quickly.
Pretty much everyone I know, Virgin or otherwise, has had their monthlies go up a fair chunk lately though. My parents are on Plusnet and theirs has just gone up by several pounds a month as well. So you might not be better off elsewhere. (Although it is worth checking, and you might benefit if you can switch to an introductory deal, or indeed threaten to leave and see if VM will offer a buyback deal to keep you.)