Buying car from UK

Q1 Are you registered as a Belgian resident, presumably you are and if so you will, eventually, be able to register the car.
Q2 How are you going to get it to Belgium? On a trailer is probably the only feasible way.
Then you will have to ensure that it conforms to Belgian regulations, changing the headlights (not cheap but keep the old ones in case you want to send it back at some stage), fitting a fire extinguisher, etc, and obtain a Certificate of Conformity which the current owner almost certainly won't have and for which the manufacturer will charge a small fortune (considering that it is only a small piece of paper).
The car will have to pass a Controle Technique and you will have to go to the DIV in person at a time when a Custom's officer is present and with all the car's papers including the insurance certificate (it can be insured pro-item on its VIN) and, of course, your eID card. Once the DIV have registered it, the rear numberplate will arrive through the post (payment on delivery), you have a front plate made, fit both plates and, at last, you can drive it on the road.
Finally, road tax and insurance will depend on what Region you live in but neither will be cheap - and, as a RHD vehicle, this expensive car will have next to no resale value.

Use the search feature - questions about importing cars pop up quite frequently.

I hope Becasse has put you off. It really is not a good idea.

Q - Will it be good idea to buy from Uk?
A - No it will not.

forget in general a car of that age, all cars below emission EURO norm 5 will be banned in mid-term in whole of Europe. BE started this month with a ban of EURO 1 and 2, this model has a maximum of EURO 3.

Get a car with mininum EURO 5 or best EURO 6.
I would nope spend money and admin difficulties into such an old one, which will be (maybe) worthless in 1-3 years.