Low download speeds following FF upgrade from 300 to 900

Wonder if anyone has had this experience. I recently upgraded from Full Fibre 300 (Open Reach) to Full Fibre 900 (City Fibre). Although the upload speeds are OK around 800 Mbps the downloads speeds are only around 350 Mbps). Been round the houses with Zen support but they say they can't see anything wrong and I would need to pay £90 for an engineer to visit. Tried another router and PC but still get the low downloads speeds. Any thoughts? Thanks

They have a 505 min speed guarantee, so I would hold them to that and its not much of a guarantee if you having to pay to get it resolved, if they cant meet that obligation, then use it for penalty free exit.

Assuming this is wired of course.

How different are the two PCs you tested with?

If they have similar hardware and/or antivirus configuration, then try booting with a Linux live USB stick and testing from there. Just to rule out "it's Windows".

Based on previous experience it is likely their end or routing

I had similar issues when I moved from ADSL to FTTC on Plusnet - in that case their equipment was still rate limiting based on ADSL speed and they fixed it without any hassle


Reminds me of issues lots of people were seeing several years ago - see thread - Slow speed after GEA migration.

At some points I was getting worse download figures than I had on ADSL, but max upload figures - they fixed it without visit.

The reason I've not taken any offers up with Zen is I don't want to be tied into contract - after last support call I don't want to be locked into contract and forced to deal with it - but line has been stable since so not jumped ship.