Virgin is a dia sham from what I read on the isp ratings on the Dslzoneuk website click here
Don't go to tiscali they are even worst from what I have heard.
go to samknows click here and enter your details, it will tell you what other LLU services ect are available to you.
If how ever there no LLU services in your exchange, I can highly recomend an Entanet reseller such as ADSL24 or Falconnet (I'm with Falconnet) for £19.99 30/300 a month you can have upto 8mb Broadband, no traffic shaping or traffic throttling. I was previously an AOL customer but I sacked them on a fixed 2mb speed, but with Falconnet its been amazing the speeds I'm getting are 6.5mps to 6.7mps!! No slow downs whatsoever. UK Based freephone support number!! Oh and monthly contracts!
You could also benefit further advice from the experts on click here
Best of Luck