I'm going to have to be careful here not to breach any forum rules....
You are using wireless, even 3x3 802.11ac, while it might have 1.3Gbps on paper in perfect conditions, in reality is nothing like that.
This is a review of the R7000, which you say you are using.
Average 5 GHz results are a different story, with the R7000 taking top places in both downlink and uplink charts with results of 248 Mbps and 232 Mbps, respectively.
Yes, it's fast, but on average it's slower than the 330Mbit your service is provisioned at. That's average, so I can easily see how it might be slower than that at times, 160Mbit does not seem out of the realms of possibility.
Next, minimum speeds. Virgin have capped your modem to 330mbit. If you have 12 channels, there is ~456Mbit available to it, if you have 16 channels, there is 608 available to it. The 330 is equivalent to your Sync speed on fibre. Other providers offer a guaranteed minimum sync speed. Virgin do too, they give you 330.
Real world throughput no provider offers assurance over. If you want that, you need a leased line, be prepared to spend £1500 a month or so for 300mbit.
You are, like me, paying ~£50 a month for 330/21. At that price it's not always perfect.
The SH3 does have latency issues due to the Intel chipset - this is an Intel bug that Intel are supposedly working on and is not limited to VM. Hopefully this will be resolved soon.
All in all it feels like you're just whining. If you want CCNA qualified network experts on the helpdesk, switch to AAISP. They are excellent, their support is... amazing. They are also expensive, and if you come up with how you want to take them to CISAS over every little issue they will probably sack you as a customer...