Hi there!!
I just wanted to add my two pence in!! lol
I was faced with the same decision as you last year. I wanted to be a bit more proactive about security, before I became a statistic!
To start with I changed the UPVC door locks to Yale anti-drill, anti-pick locks which cost less than £5 each from a local glazing firm (they cost about £25 in DIY shops) and they took less than 2 minutes to fit.
I also don't like the sight of wires, so a wired alarm would need to be professionally installed.
Basically no one would ever advise you to go wireless if you can afford to go wired. There are so many pitfalls to wireless alarms. False alarms, the signal can be jammed, batteries need replacing after a year etc.
But I just didn't want to spend hundreds of pounds for an alarm system. If someone wants to come in, they will no matter what security you have installed.
I just wanted to put off the opportunity thieves looking for an easy target (with no alarm box), at a minimal cost to me.
After doing lots of research I ended up spending about £25 for a brand new wireless alarm from ebay (about the price of a dummy box for a wired system).
I ended up with the Response Alarm SA5. It features an auto dialler so it calls me when the alarm goes off. The control panel is mains with battery backup which fits my requirements and it all has anti jamming technology which is supposed to sound a full alarm if any of the components can't talk to each other. It also features zoning with each sensor being on a different zone, great for fault finding in the future.
The other plus side is that everything comes as a kit inside a box, so it is all desgined to work together. And everything needed to fit it is included, including the batteries and wall plugs!! - Drill not included though!! lol
I installed the whole lot in about 2-3 hours and it looks good (no wires). I have never had any false alarms from it, so I can highly recommend the system as a cheap alternative to wired. But I would never pay retail price for it, which is almost daylight robbery itself at just under £300!!
Also, I didn't want to use the magnetic contacts that came with it, so I flogged them on ebay at £15 a piece and ended up making a profit!!
I know being wireless, it isn't the perfect solution. But for me, the right deal came along at the right time...