How can I convert my UK driving licence to a Belgian one?

And will I keep my class C1 category if I do so?

I don't know why you would want to convert it even if you could.

The UK driving licence is reckognised in most parts of the world, keep it as it is, is my advice.

why dont you get an international driving licience - valid for 1 year or are you staying longer

Your licence is valid in all the EU. If you move to Belgium, think about taking a test there if an exchange is not possible.

Are you living in Belgium permanently, or do you intend at some stage to return to the U.K. If the first part answer is 'No' and the second part answer is 'Yes' then don't bother changing it. Your U.K. licence is as valid there as a Belgian Licence.

P.S.
International Licence NOT required.

Your UK licence is valid providing it's the plastic photo licence, you should carry the paper part with you as well. Under EEC laws there is no longer an obligation to change it.

as with all countries basically your licence is valid for 12 months and then you have to take a test in the country you reside in you cannot under any circumstances convert your licence into one for a different country. this first answer to the first half of your question also answers the second half of the question yes you will lose C1 cat. but your british licence is also valid in the uk until the expiry date they dont have C1 cat in belgium

I don't know if you can use your UK driving license in Belgium but I do know you don't need an international one.
We have an European license so I suppose that, if the EU sign (circle off (blue) stars or the letters EU) is on it, it's OK...

Go into the local municipal offices (in Dutch they are the Gemeente) and ask them how you go about it. They will know.

You can drive in Belgium as well as I, a Belgian can drive in the Uk.
The only thing is that you Must respect the traffic signes and drive on the right side of the road... not the left as in the UK.. and give right priority and not left

your licence is valid for Belgium

If you have a photocard-style UK driving licence (+ the paper sheet), then it is valid in all EU countries until your 70th birthday. This is why they standardised the format and category codes between all EU countries, so they don't have to be in all the different languages. There is no need to exchange it for a Belgian licence if you don't want to, and no need to notify the DVLA that you've moved abroad. You do NOT need an International Driving Permit.

The second link below explains the rules applying to foreign licence holders who have moved to the UK, and as you can see, Belgian licences are valid until the holders 70th birthday, or 3 years after they move to the UK, whichever is the longer period. The Belgians will have similar rules, consult the local council/commune for advice.