Wireless will certainly be a lot less messy and quicker to install.
Many burglars gain access through upstairs windows, so yes, these need to be alarmed.
I recently put in a hybrid HKC alarm in my own place to replace a wired one. That allowed me to add wireless sensors in the garden shed and re-use the existing wired sensors. Siemens systems also get good reviews, but I believe these are more expensive.
A dialler (or digi) will dial one or more pre-set numbers with a pre-recorded message in the event of an activation. You can get land line or GSM diallers, the GSM variety are more expensive and will need an active SIM.
If you're going down the dummy alarm route, you'd be better off getting an actual bell box (SABB) and attaching a 12V supply to it so that the status LEDs blink. Looks far more convincing than the standard dummy boxes you can buy.
CCTV should be secondary to an alarm. A regular hoodie will render CCTV useless, also, burglars who are aware of the presence of CCTV are likely to go for the recorder.
Keep in mind that any company/person you hire to install alarm equipment must be registered with the . You are breaking the law if you hire someone who is not, with a fine upon conviction of up to €3,000 and/or a prison sentance of up to 12 months.