Air con has been topped up to pressure blows hot ok but is not cooling on cold only a slight improvement after topping up

Is compressor clicking on and off?
If its not here is alist of items to check out:
-pressure switches
-compressor
-on/off switch
-a/c relay,
-cooling fan relay
-cooling fan
-control head
Remember there is no such thing as just topping off. The refrigerant doesn't evaporate. It is in an enclosed system air tight always under some pressure whether on or off.
So if someone told you that you were low on refrigerant what they should have explained this to you. Basically you may have a leak.
If you have a set of R134A manifold gauges put them on and ckeck for refrigerant being present in the system. If your below 50 psi on high side you probably have a leak. Checking for leaks on a 2003 is not so bad .First try looking for oil spots on the refrigerant line . If that doesn't work then bring the vehicle to a repair shop. they have the proper equiptment to do this. If you do find the leak via oil spots you have to recover the refrigerant thats in the system with a recovery machine first. Then replace the o-ring at the connection that was leaking or remove/ replace the item that was leaking.
Your gonna need a vacuum pump or recovery machine for the next part. Pull a vacuum on the entire system for 20 minutes then shut off the system and check for leaks. If manifold gauge on recovery machine doesn't move within five minutes you can recharge the system. Good luck

Check your refregerant pressure, if it is ok, clean the system, replace filters and valves