Reinvesting profit as a non incorporated company

[camccarthy@statestre]

I am a top rate tax payer and am getting into buy-to-lets and plan on building a portfolio of properties over the next few years. I plan on keeping these properties over the long term. I have researched this area and came to the conlusion that a limited company was the best option due to 0% tax on profits under 10k and the ability to invest company profits in new properties without paying tax. However, lenders are offering much less competitive rates if I buy through a limited co.
Q. Is there a way to reinvest rental profits from buy to let properties in a tax efficient manner (i.e. not paying 40%)if I am not doing this through a limited company? If I can show that all rental profits were put towards a deposit for a new property can I avoid income tax on them?