As far as it goes the response answers my question, but it uses the word arguably, I would have expected a case reference that I could use in my defence at a hearing, without that your 'consultation' has no value..
the Court of Appeal in RTS v Molkerei Alois Muller considered whether a "counterparts" clause, specifically stating the contract would only become effective once all parties had signed and exchanged it with one another, prevented the contract from being entered into. The case involved the manufacturing of yoghurt pots. RTS was the manufacturer and began production on the basis of an agreed letter of intent between RTS and Muller. The parties then continued to negotiate the terms of the draft contract, which incorporated the following counterparts clause:
"The Contract may be executed in any number of counterparts provided that it shall not become effective until each party has executed a counterpart and exchanged it with the other."
The draft contract was eventually drawn up, but never signed. Around 6 months after the letter of intent had expired a dispute arose between Muller and RTS where Muller refused to pay. The question remained whether the draft contract, even though unsigned, had been entered into as a result of the parties' continuing performance. The Court of Appeal (overturning the High Court's ruling) believed the counterparts provision was clear: the contract could not come into existence until the parties actually entered into the written agreement.