A student asked this today. (They do). I said:
Yes, I recommend sitting your theory test before more lessons. Theory work benefits practical lessons, and practice gives theory a proper context (and therefore memorable meaning). See www.trc11.uk/Theory for guidance.
As for practical tests, people often ask about differences. There are some. The DVSA work hard to iron these out, but ultimately it's the nature of the roads around the test centre which has the biggest influence. DVSA's advice is "if you drive to the right standard, you will pass the test". They routinely publish statistics, for the whole country. Birmingham has two test centres with pass rates often in the bottom ten (out of 308!) See these from the last line of http://www.trc11.uk/centres.html
That latest table will show you where Bournemouth fits. Don't read too much into the figure. More will depends on time of day, how you're feeling that day, how familiar is your environment. You can look up its postcode and, on computer, look at its outside, plus all roads for 20 minutes around, to see what you think. I'd be surprised if someone hasn't also put on YouTube sample videos of lessons or mock tests around Bournemouth.
Good luck, and let me know how your thinking goes. Come at me with more questions if they arise.