In my dictionary:
downlight down lite, n, fire hazard.
It IS possible to install downlights safely, although that seems to be beyond the coordination capabilities of the various disciplines involved in the overall construction process.
But, whatever the pros and cons of the lights themselves, the quality of their light, the installation process, the installers, the requirements of the Building Regulations and the Wiring Regulations, etc, one thing is certain: buying the lights because they are cheap is a sure-fire way of getting off on precisely the wrong foot with everybody involved.
Wait until after the holidays, when sales-fever has subsided and pay a proper professional the right money to do a safe job. (The right money is, by the way, much, much more than you may be thinking. If the installer will do it cheaply he doesn't know what he is doing.)