With Express you don't actually have an Instance of SQL Server installed, it's a bit like access in that you just drop the .mdf and .ldf files for a database into your web folder. So the contention with other users of the hosting partners server is no different from any other file type.
Lots of ASP.NET 2.0 features rely on SQL 2005, in fact many features automatically use SQL express, so unless you have MSSQL access you lose a lot. There are lots of hosts out there that provide Express free or at reasonable rates, i'm just asking for reccomendations not M$ hating.
As said in my original post this is not for commercial stuff, just as a testbed for my own purposes so don't want a dedicated server or VPS but I am happy to pay a bit more ie £150 a year sort of figure.