no terms and conditions

I have been consistently paid late by a customer, the invoices I sent were generic and didn't have the customers details on them and no payment terms were agreed, they started paying late and then I started adding please pay within 30 days on my invoices, it got to the point where they owed me 4 separate invoices and I e-mailed them saying please pay me asap I don't want to have to add charges. They never paid so I sent updated invoices with £40 charges on each one. They have since paid but without the charges and our working relationship is no longer. Can I actually claim these charges and also charge for all the late invoices since I started working for them (jan 2014). When I said thank you for your partial payment after they paid without paying the charges I was told they hadn't seen my terms and conditions and if I provide them they will happily pass them to their solicitor, where do I stand? any help will be gratefully recieved