Hi - Myself and my team of 2 developers have great experience in just this area; specifically building, or rebuilding web applications from the ground up using the latest .Net technologies, SQL Server and leveraging open source projects - jQuery, Ninject, Elmah, T4, SignalR, Dapper, Subsonic, Twitter bootstrap, Castle Windsor - to name but a few we've used recently.
We have in depth knowledge of ASP .NET, Javascript, SQL and HTML5 and could deliver this project quickly and efficiently by using the Agile technique for sofware delivery .
Together we have recently built web applications for the construction business, for bug tracking, for time management - links can be supplied on request.
Without knowing exact requirements it's hard to make a call on architecture but I would envisage an ASP .NET MVC3 application using Entity Framework (or similar), SQL Server 2008 R2 back-end and Bootstrap Toolkit for UI.
Additionally, we are also based in the UK.
Hope to hear from you.
Regards,
Graham