So it's not BT after all. It's Hyperoptic which is a London based fibre system. I've done a speed check on each floor and they work out as follows:
Ping. Download. Upload
Floor 1. 41. 26.7. 25.5
Floor 2. 104. 28.6. 23.5
Floor 3. 61. 25.8. 14.4
Floor 4. 69. 22.1. 7.4
The router is on floor 1 and he is supposed to get 80 mps. The package is called 1 Gbps which is a bit of a misnomer to me!