So, the outcome here after a very long Telephone Conversation with EE's Tech Support and a lot of Music on Hold whist Tech Team do some cross referencing with CS Billing is that I am correct in All of the reported issues in my original Post.
Tech Team have confirmed that It seems that EE have forced my 5G UL Plan from a 5G Connection and only allowing a 4G Connection to that particular Plan, and in addition, have Speed Capped the Plan to well below the usual 4G Speeds with a maximum cap of around 100mbs max. TS also confirmed that my Plan was changed a few months back by EE without any confirmation of a Plan Change from myself, this apparently was due to a Smart Benefit issue (Prime Video) but more on that at some point.
Apparently the reason for the loss of 5G and the 4G Speed Capping is because of a Breach in EE's Data Fair Use Policy (FUP) although Tech Support did confirm that my last few Months of Data Use was only around 100Gb or so each Month, so still unsure where the Breach is, there was some discussion around using Netflix as a Smart Benefit usage on the Plan (now my replacement Benefit to disconnected Prime Video), but I was informed that a Smart Stream Benefit like Netflix / BT Sport etc does not eat into your Data Plan as it has its own UL Video Data use allowance whilst its being used as a Benefit (even though the Overall Plan is Unlimited). Another factor could be excessive Data Gifting from the UL Data Plan but again Tech informed me that this should not effect or be taken from the FUP amount, but not so sure on that one if honest.
All I do know is that all of the above issues have only recently started occurring since EE Changed my Plan from 5G UL + Smart Benefit to now a 5G Allrounder Plan a few months back, and although I do regard myself as Low to Average Data User I'm fairly sure I would have hit the FUP at some point here and there in the past (especially during Lock Down) and have never had any issues at all during the pervious periods in the past prior to the unknown Plan Change.
