So I've swapped out the 20 quid 'TP-LINK TL-WA801ND 300 Mbps Wireless N Access Point’ and replace it with the 'TP-LINK T TL-WA1201 AC Access Point, 867 Mbps/5 GHz + 300 Mbps/2.4 GHz' - more money, more antennas - it's gotta be better right? Plus I'm hoping it's that 5ghz WiFi capability that solves my speed problems.

To minimize WiFi interference I've placed the access point on the far side of the room to the router and run a gigabit ethernet cable around the edge of the room.
The access point actually looks quite nice in position -
So I've got a 5ghz 867 Mbps WiFi client connected via gigabit ethernet to a router serving 10 or so internet connected devices - either wired in via a gigabit switch - or connected to my own 5Ghz WiFi network.
In terms of installation - it's a pretty straight swap. Hook up the new access point - change it to AP client mode and connect to the communal 5Ghz WiFi network. Then switch this out with the old access point and I should be good to go.
Let's look at some speed test results -



So in short - from my perspective problem solved. Internal network speeds for media streaming across the network were obviously without issue - but what's the point in a 100Mbps fibre connection if you can't take full advantage? I've now got a nice speedy connection, with an ad-blocking PiHole where I control the traffic. So in short - I win! And lesson learnt - don't skimp on hardware!
This stuff is all pretty simple - but if anyone wants any tips on similar projects - get in touch.