BT Infinity 2 but only getting 16 Mbps wired, can ...

Question

I just got my BT Infinity 2 installed today. After running several speed tests on a wired connection via a ethernet cable, it seems my download speed is set to 16 Mbps and my upload speed to less than 0.6 Mbps. Considering the cost of BT Infinity 2 is quite high compared to the next best one, is it possible I can downgrade but still get the same speeds?
When I enter the also newly-installed phone number in the BT Speed Checker, it tells me I can only get up to 8 Mbps downloads. But when I claim I don't have a phone number, and just enter my Flat # and Post Code, it tells me I can get 16-20 Mbps downloads. I don't understand why it's giving me two numbers. 
It's a bit sad I'm paying for up to 75 Mbps speeds but I can only get 16 Mbps even when wired. And actually when I ran a speed test wireless, I was getting the same speeds of 16 Mbps. I'm in the same room as the Hub so maybe that's why. No other connections are using my wireless either. Not even my phone atm.
Either way, I guess I want to know the answer to either one or both of the two options:
1)Why am I getting only 20% of the "up to 75 Mbps speeds"? 
and/or
2) How to go about downgrading to maybe BT Infinity 1 instead of 2 so I pay less but still get the exact same speeds of 16 Mbps?
P.S. Is it possible my speed will increase over the next few days? Since the Post Code speed test said up to 20 Mbps, I'm assuming that's as high as it can go...

Answer 1

Featured ProductsDownstream Line Rate(Mbps)Upstream Line Rate(Mbps)Downstream Range(Mbps)Availability Date  High Low High Low    
FTTC Range A (Clean)
21.7
15.5
3.2
1.6
Available
FTTC Range B (Impacted)
18.6
8.8
2.6
0.8
Available
WBC ADSL 2+
Up to 2
1.5 to 4
Available
WBC ADSL 2+ Annex M
Up to 2
Up to 0.5
1.5 to 4
Available
ADSL Max
Up to 1.5
1 to 3.5
Available
WBC Fixed Rate
1
Available
Fixed Rate
1
Available
Other Offerings
Fibre Multicast
Available
Copper Multicast
Available
Wholesale speed test:
Ethernet connection via bthomehub.home Troubleshooting > helpdesk : 
1. Product name:
BT Home Hub
2. Serial number:
+068343+NQ42355023
3. Firmware version:
Software version 4.7.5.1.83.8.173.1.6 (Type A) Last updated Unknown
4. Board version:
BT Hub 5A
5. VDSL uptime:
0 days, 06:02:33
6. Data rate:
642 / 16957
7. Maximum data rate:
657 / 17365
8. Noise margin:
6.4 / 5.5
9. Line attenuation:
0.0 / 32.7
10. Signal attenuation:
0.0 / 26.5
11. Data sent/received:
46.8 MB / 739.8 MB
12. Broadband username:
[email protected]
13. BT Wi-fi:
No