I have 2 offers to join exec MBA programmes: Cass and Imperial.
I am from an engineering project mangement background, looking to change careers and move into consulting.
In the long term I plan to start my own consulting or project management company
Which one is best for these objectives?

I'd say Imperial but why not LBS?

Why Imperial? I am leaning towards choosing Cass.
Imperial seemed to put a big emphasis on it's entrepreneurship project in the second year
Haven't applied to LBS as the fees were so high, also I was looking to start in March/April this year and have not studied for the GMAT yet

Cass is a great school for finance. If you're thinking of starting your own firm, then Imperial is great not only because of entrepreneurship but also because it's in the habit of taking engineers and turning them into MBAs. Imperial is also much, much better at getting grads into work. True, Cass has a higher average starting salary because of its finance students, but Imperial is going up in the rankings and get more alumni recommendations in the FT ranking.