I've got a Tom Tom One which I'm pleased with but as it's the only one I've ever used I can't comment on other models. As you can see, we've all got our favourites.
If you can wait, I understand 'Which' magazine are reviewing Sat Navs in their December edition - if you don't subscribe, most libraries would have a copy. They're very thorough in their testing and I would be happy to accept their guidance. You need to decide what exactly you want the Sat Nav for, is it just to get from point A to point B, or do you want all the 'bells and whistles' with speed camera alerts,and traffic and weather reports.
Most Sat Navs let you put in a full address or a post code. If you can get a post code for your destination address then I would definitely recommend this method.
When I first had my Sat Nav I made the mistake of entering Abbot Road instead of Abbots Road in Birmingham and finished up about 7 miles from where I should have been, since then I make every effort to find the post code! It's also normally quicker to set up a Sat Nav this way.
Don't worry that you won't be able to use it, as RIAS says it's strictly logical to use.
One final thing - don't leave on display in the car when you park up.