You cant go and remove things you fitted. He can then do you for theft/vandalsim etc. Just cos you fitted them you are not entitlied to do this.

Ive been here with late payment and im afraid unless it is stated in writing that they must pay you with XX weeks/months etc then you just have to wait!

When i quote for work now, i always put on the bottom of the quote that our payment terms are strictly 2 weeks from issue date, if you accept this quote then you accept our terms.

They have to pay you then or you are legally entitled to charge interest!