Speed loss using L2tp vpn

[RJH]

Hi. Have no experience of vpn and hope this is the correct forum, Mod please move if not. Thanks.
With Virgin on a 50Mbps connection, have signed up with Strongvpn and connected with L2tp. Can anyone advise what the throughput penalty should be please?
Thanks.

 

[RJH]

Thanks both, I can use open but that may not mean a difference in speed, currently achieving between 7 & 12 Mbps on a connection that is normally running at 48Mbs +. The server is in Canterbury, maybe 20 miles away - pings 20ms.