I'm afraid you will find it very hard to sell the property without visiting it or meeting the respective local Estate Agent. This is because-
1. They will need to verify your identity.
2. They will need to be handed the keys.
All I can suggest is that you pick a nationwide Estate Agents (a Dixons/Bairstow Eves for example) who may have an office near to where you live and also an office near to where the property is. You could then give instructions to your local Agent who could pass it on the Agent in their other office which is near to the property.
(Even if you were to use an internet based Estate Agents, they would still need to meet you at the property).
I hope this assists and sets out the position.
Hi, can I assist any further? If not, I would be grateful if you could rate my answer. Kind Regards Al