Slow wifi t800 (but not on my note 4!)

Hi As per above, websites are taking an age to load or do not load at all yet my Note 4 runs perfectly on the same wifi and at the same time/same site - I've tested both simultaneously.

I've cleared the cache and done the usual stuff. reluctant at this point to do a factory reset as it takes so long to recover android devices.

Any quick ideas to try?

Strangely when I've run a speedtest it show similar to the phone!!!!

I'm on 5.0.1. UK wifi only T800.

thanks