Reopening Victorian 2 x Victorian fireplaces

The vent is there to be a vent. Strange but true. The best thing to do is as carefully as possible remove whatever is closing the hole at the moment, usually a timber or plaster board of some sort. Then look up the chimney, usually you will be able to see any blockages, or use a torch to check. If there is a bird's nest, which is more common than anything else, get a chimney sweeping kit and clean the chimney. Make sure that the brush comes out of the top and that you can see it from outside. Do this with both chimneys. Once you have done that you can put in whatever kind of fire you want so long as you have the relevant kind of flue, especially for log burners etc. The electric socket and aerial socket, assuming they are all external to the chimney can stay put. If their wires are inside the chimney they need to be removed to the outside of it. As you will not be doing anything that contravenes any electrical rules and regs, you can do this yourself if you know what you are doing. If you don't, get a sparky in.