Why would my speed suddenly drop...?

[CoPHostage]

I did some jiggery-pokery with the router (Hub 3), so that I could move the 2.4GHz to a separate channel in order to reconnect a device which doesn't support 5GHz. Prior to doing so, I was getting a consistent down speed of 40MB/s (megabytes not bits), no great shakes for some, but it's the fastest down speed I've ever had. I don't know what package I'm on as I don't pay for it, but I believe it's probably M350. 

Anyway, I thought it was a tad slow, and I've just done an Ookla test, and it's dropped from a steady 320Mb/s down to just 72. 

My Mac is connected to the 5GHz band, and my iPad to 2.4GHz.

Help a thickie out here, would separating the bands kill the speed...? Upload is 26Mb/s. 

If not, any ideas as to what's causing the sudden slowdown...? I don't know the name on the account so I can't access it. I have rebooted the router, not helped one iota. Could I have inadvertently changed something in the settings to cause the speed drop...? 

If it matters I'm in Bristol, so hardly the middle of nowhere. 

[CoPHostage]

Now I really AM confused. This is the speed next to the entry for my Mac in the router settings. Does this mean that it's supposed to connect at 761Mb/s, (which would equate to a MB/s down speed of 95)...? I'm really not feeling at all intelligent at the moment. Someone help me out here!

[Adduxi]

Splitting the SSID will not affect the speed.  However, 5Ghz is the fastest but less distance and penetration.  2.4Ghz is the opposite.

[VsUK]

Relying on Virgin's wifi as your only source is good enough for average use, but it's basic at best. There's no way they can cram all those features into a router & give it away for no cost to use their service, there has to be some drawback & that is, it really can't cope very well with multiple connections currently active at the same time. I often saw my wifi just stop for no reason & then start again. So, I switched it into modem mode & hooked up my own router as the wifi source. It acting as a modem removes all the features other than decoding the signal to give you broadband & the hardware makes it more than good enough as a modem only, not so much as a wifi router. 

But, would be nice if I had internet, not had it for 6 days now, going onto 7. If I have no for much longer, I'm done with Virgin.