Probably the best thing to do is to get three quotes. I would advise that you pick three accredited companies either ssiab or NSI gold
https://www.nsi.org.uk/ https://ssaib.org/ you can search for local companies with your postcode on these sites
Any good company will be able to tailor the alarm system to your needs and will give advise on how to make it simple to use.
Most companies will have their own preferred brand that they like to install, we could all start recommending different brands here but it would just confuse you if installers in your area dont use these brands and recommend something else.
Once you have your quotes come back here for more advice if you need it