All the advise above regarding positioning seems very sensible hard to say from not seeing the property.
Yes it is true that Risco doesn't get a lot of love from many installers here and you are correct that everyone had there preferred hardware, there are many reasons that contribute for this, every company is different.
Generally I would say that Risco is like Marmite. Some places it's all they fit. I personally avoid the stuff, they can be a headache to program, missing some features for me and contacting Risco directly for parts which can be an issue if urgent.
One positive with the Risco gear is they use the same batteries throughout, although this does mean chunky contacts as above.
I personally lean towards fitting hybrid systems with a wired bellbox and wire as much as I can but again this is just a preference.
As a end user you should consider the alarm as a service not a product, the system will need maintenance. You need to be comfortable with the company, the product should be less of a consideration in this scenario.
Asking a company to fit something else will only lead to a headache they may not be trained on it for example.
I would say the general advise here is get at least 3 quotes, consider all there points and go with the company you feel most comfortable with, not just the cheapest.
If you are still most comfortable with the company above then it's the right way forward for you.