Which bit do you need to keep - the disc or the hole? More on that in a sec, but first, about that specific router:
The first thing to do after you get one, is to take the cutters that come with it and put them straight into a metal recycling bin somewhere. I bought a Power Pro* one from B+Q years ago, which was very similar price (and the cutters look identical). The V-groover was ground asymmetrically (how do you actually manage that?), and far too dangerous to even spin up in the collet. The electronic speed control died and the plunge lock, and the bearings weren't wonderful either. BIG HINT:
B+Q and Screwfix are owned by the same company. Yes you can, but if you pay a bit more for a better quality router, you won't be paying twice over the longer term - Makita, Hitachi, Trend, Bosch, CMT, DeWalt - they all sell good quality machines.
Get cutters from Wealden or Axminster. Trend, Freud, CMT and Titman are also good (I'm sure there are others, but those I have used). Bear in mind that each edge of the cutter hits every bit of the workpiece several times (unlike saw blades), so if it's not up to the job, you WILL see that in tearout or burning of the work. It's really not worth attempting to use cheap cutters if the finish is important - there are no magic tricks to make cheap/blunt cutters cut better. Upcut/downcut ones will leave a better finish, because they shear the fibres rather than hitting them like a chisel. They are harder to make and more expensive but IMHO worth it for the finish and because they last longer too.
. . .
Is this a high volume job - say 50 discs of each size, or one or two of each? Different techniques for different purposes. Also, how good does the accuracy and roundness need to be?
For example, if making lots of same-size discs, consider a bandsaw as a starting point.You can stack your blanks and cut quite a few at once. It's safe and fairly easy. You're not limited as to diameter, either (for small circles you just need a smaller blade, and to go gently). You could use a jig, or freehand it for bigger circles, and finish up with a sander or router to smooth around.
Make one good jig (smoothed and nicely circular), and use that to finish them - your router would be lightly loaded and you'll get a much nicer result. Double-sided tape would hold the template in place, and you'd need a
bearing-guided cutter. As you can see, good ones are not expensive, and the "
down-shear trim" ones will give a better finish.
From my limited experience, using a router trammel works better the larger the holes are you need to cut. The accuracy and to an extent the finish quality are determined by how good the centre pivot is, and you do have to fix that to your circle, so there will probably be a mark or hole(s) left behind. Small discs are a challenge if you want a good edge finish (bandsaw + sanding for me!). Whichever you choose, if you're using a router, fix down both the inside and the outside parts (no matter which is scrap), so that nothing moves when the cut meets.
Hope that helps,
E.
*or Performance Pro, or Performance Power (or possibly even Peter Pan) - honestly I can't be bothered to go up in the attic to look.
