The main problem as I see it is that he needs the TV to be able to plug in the headphones he has, Yes Tug fanatics Idea would work but, in this case, having read all the previous issues around this small problem just makes things more complicated for regiment and could result in wires all over the place depending on where any HIFi unit is.
Solutions have been given but do not seem to have been acted on or are not practicable for this situation.
We now seem to be looking for a size of TV before the initial problem with the headphones has been sorted!!
Regiment NEEDS to try to visit a shop with the headphones he wants to use, Currys will do that as I am sure most small retailers will as well, unlikely any of the large supermarkets will as they generally do not have staff who understand the Tech.
If I lived close, I would go and get it sorted but unfortunately too far away.