in a word nope, no one can. Especially Virgin (who of course will officially deny there is an issue saying the service in the area is fine). But that doesnt mean actual speed is.
Just look through all the posts on here regarding the subject.
In a nutshell the old setup of Virgin/EE was excellent the new setup of Virgin/Vodafone has performance issues in some (many) areas.
And we are also all in the middle of Virgins move to O2 (despite only recently moving to Vodafone). So I cannot see the infrastructure provider put much effort into rectifying it can you.
If I was on a mobile contract with Virgin where I pay monthly I would be cancelling and moving to EE (even though it may cost a bit more). But my mobile is included within my Broadband Ooomph package so technically it is 'free' so the option to take out an EE contract would become an expense I can do without.