Agree OP should look at the range of options, hence knowing what is important to them (latency? Bandwidth? Download caps?) is key.
Mobile data might be an option, but unlikely if low latency (eg gaming) is their priority.....
In a variety of exchanges, Sky and other ISPs have a range of equipment in the exchange that they use to provide their networks. Not all equipment is OR maintained. Plusnet and TTBs equipment is more likely to provide slower speeds etc
Unless this issue is OR here... ADSL is being phased out and might not be appropriate
I think the OP should consider 4G alternatives
Vodafone and H3G might be an idea... I get 60 on H3G down and 80 when I tested on Voda...
They now offer UNL packages...
Where does the infrastructure diverge from ‘common’ (Openreach) to ‘distinct’ (Plusnet vs Sky)?
Where is the “rate limiting step” here?
If the quality issue arises in the ‘Openreach’ part, if that is the rate limiting step : how does e.g. a different router improve speed?
Update. No update. Still waiting for anything from anyone with regard to cca request. With regard to the ppi I have received acknowledgement that ppi did exist on this account. A couple of letters saying they needed more time and today a letter from mbna saying they currently don't have enough info to fully assess my circumstances at the time of the sale and could I just fill in an 8 page questionnaire so they can complete their investigations quickly. Now are they trying to trip me up and wriggle out of paying or should I complete and return. They ask questions such as my income at the time which I wouldn't have thought was relevant to ppi. Thoughts please?
Don't touch them owe me £500 since January 2019 make excuse after excuse. Seem they always have software problems sending money out. Keep saying they will call back or email nothing been chasing it now for 6 mths the phone staff always have the same banter we will chase it up and get back to you then nothing!