small problem with plasterin is you cant really add 'add materials used therin remain the property of 'insert company name'' etc..
something along the lines of 'reasonable standard of workmanship' and quote some bs number...
another thing to be aware of is most terms and conditions dont stand up in court unless its written out by a lawyer..sorry solicitor (bleedin yanks)...ive never ever had a problem gettin paid, its too simple a set up, theres no real complications to exploit...i dont even bother with em, but if i did it would only be to look more 'professional' and it'd only be something like 'customer to pay agreed price as agreed and signed for on completion or within 7 days of completion'... or if you want stage payments, say so, get em to sign it...easy.
if you get a nobhead you'll soon get an inkling in which case put em to the test, ask for a stage payment, if you dont get it, dont go back, if they dont pay you to get you back its one of two things...they aint happy with u or theyre a dodgy git, either way cut your losses..