www.nightvisionforumuk.com

Hello, I'm writing you from Belgium, just bought a low budget Hatsan AT44-10 5,5 mm with a Hawke 3-9*40 scope, hoping to make pestcontrol fun.
Step by step I'd like to build a NV system on it for nocturnal ratting and scaring the occasional ex-wife.Joke,just to make sure...

Welcome to the forum, you'll find all the information you need here although can't help with ex wives, sorry.

Hoping not to throw any one of with my amateurism , but from what I understand , IR scopes are a bit better than image intensifiers because independent from ambient light , they work much better when combined with an illuminator , IR lasers trump LED's when it comes to distance , but they need a lens to spread their focus . how is it still possible to combine a IR laser to aim together with an IR laser to illuminate if one chooses to do so ?

There are uses for both digital devices and tubed, it depends on what shooting you do. Digital is fairly simple to build yourself and can be done for low cost. For illumination most people prefer led torches to lasers, both can be focussed and again led torches are easier to modify at home and they normally give a more even beam, some lasers can produce a beam with light and dark areas.
Using a laser to aim with nightvision can be difficult as the laser is often too bright and obscures the target.
What sort of night vision shooting will you do?

mostly magpies , ravens and rats , after time I might expand to rabbits,

You already have a scope, so build an add on unit and aim using the cross hairs.
If you have tubed NV then you can look with your goggles or monocular, have a laser mounted parallel to your barrel, then shoot by pointing the laser and seeing the light splash from the target. When the splash is in the right spot, shoot. This works for flat shooting centerfire rounds and pigs. Air rifles with a distinct arcing trajectory and small game with tiny kill zones, not so much.
An add on is the way to go for that sort of work. Watch marky's & Rolaids videos as your starting point:
https://www.youtube.com/user/Marky610
https://www.youtube.com/user/RolaidsBench