Is this a good strategy for me to get into contracting?

[hobnob]

I don't have much faith in the idea that the client would only sue the umbrella company. Clients are people, and knowing what people are like, I imagine they would think: "contractor screwed up.... therefore sue contractor." I imagine they would perceive the umbrella company as simply an administrative detail, as in "the umbrella company? Oh, they just do the payroll.".

Suppose that you were working through your own limited company, and then you deleted a database by mistake. Who would the client sue, you or your company?

If you're working through an umbrella company, the same principle applies. I.e. you (as a worker) don't have any contract in place with the end client: there will be a company in between, and the company will get sued.

So, like eek said, don't worry about it - this is the umbrella company's problem.