4G+ Internet speed behaviours

[#1]

Just wondered if anyone here has experience with 4G or 4G+ internet through a cellular modem?
I'm soon going to be in a position where I won't be able to have my own fibre service as someone else I will be living with will take the Openreach provision of only 1 line per property so I've been experimenting with some kind of alternative so that I'll at least have something.
I purchased an un-locked TP-Link MR500 and am trying it out with my EE contract 'our best speeds' 5G SIM. Initially with the 4G+ element added on to the 4G I hit a pretty much similar speed of about 80Mb/s down that I get with my current Plusnet 80/20 VDSL service but after maybe 10 seconds it immediately starts to reduce and will settle on about 30Mb/s and then at peak times it will go down even further to ridiculous single figure speeds. I just wondered if this is just my experience of 4G internet or whether it's just my own situation?
The mast I'm connecting to I'm sure is only a short walk across the road away from me as I'm seeing -79db and downwards in the signal strength area and when I look at the signal with my phone there are lots of different good signal level EE Band 3 connections flashing up and so I'm assuming EE have at least good signal coverage or good capacity here or do you need to live in an area where there is Band 1 and 7 to get a decent 4G+ service?

[#2]

Been using idMobile's cellular service and get around 30mbps, which is on the 3 network. Speed you get on a phone will different to that on a modem as they use different part of spectrum. 5G speeds from what I see are generally disappointing/ has been oversold by the cell companies.

CHECK HERE:
https://www.signalchecker.co.uk/

[#3]

For more detailed map coverage and finding the best "mast" for you home location. try this.

https://www.cellmapper.net/

click Menu

Click "Provider"  ( this gives a world wide listing of providers..)

Type in the name of your selected provider in the box

then select the "offering" !  click outside the box, then select "Search" from the menu, and enter your postcode.

You may need to click on the - sign in the box at top right of screen..

( the blue screen is centred in the atlantic ocean off west africa... so you need to zoom out to relocate the centre of the map to the UK and then zoom out to view your home location.)

On arrival at your location... you will see the masts in the area... if you now click on one, you will get the coverage area from that mast, and be able to get further information about it .

Hope that helps !.

[#4]

@southerner  I hope that the time spent in writing up my experiences, and passing on the information to you, proved worthwhile.

Unfortunately, I have not had any follow up from you. 

Did I waste my time?