switch from your Broadband providers DNS settings and try using Googles instead i.e;
Virginmedia - Primary = 194.168.4.100 and Secondary = 194.168.8.100
Google - Prminary = 8.8.8.8 and Secondary = 8.8.4.4
The Domain Name System can run pretty slowly on ISP servers - Google tends to be far more resilient
You can also consider setting your FPS to have a 60 FPS limit - if you have FPS set to maximum in high population zones it can cause your system to become very laggy