wifi issues despite sky diagnostic checks giving me the green light and saying everything is ok

[f_smith]

I have an extremely frustrating situation with my wifi. 
Current speed tests are giving me an excrustiatingly slow 0.15 mbps download and 1.4 mbps upload but when I test my connection, through the sky 'service checker' on this site it says everything is ok. It isn't. I've tried different laptops, phones and they are all absolutely crawling, often dropping connections completely. 

Please advise if you can. I'd like to get an engineer out but I'm not sure how I do that. 

[Highlinder]

@f_smith Could you please post your router stats following the link below.
https://helpforum.sky.com/t5/Broadband/How-to-find-your-Sky-Broadband-router-stats/td-p/2855717#M101...