Is it lawful in Islam to work as a satellite dish installer here in the UK?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

The rule of installing dishes in Britain or elsewhere depends on the state of those who will use it.
If the people who use it limit their use to that which is good and beneficial, then it is lawful to install it.
But if people using it will go beyond that then it is Haram (prohibited) to install it or help in doing so.
However, if you do not know the state of the person, i.e. whether he is good or bad you base your judgment on the most reliable probability. If you cannot sort out the outcome then, we believe you better avoid this work, as most people are likely to misuse such devices.
Allah knows best.