In order to take advantage of ASP.NET 3.5 support, customers on win7.pipeten.co.uk and win9.pipeten.co.uk can change the ASP.NET version in the control panel to 2.0. By choosing .NET 2.0 you should be able to take full advantage of .NET 3.5 also.
Shared hosting customers on servers other than those listed above should contact support via the hosting control panel regarding .NET 3.5 availability and/or moving your account to win7 or win9.
Please see updated UK – .NET Version Support.