A while ago I needed to briefly retain a lawyer to navigate a complex contract with my employer, there may be terrible lawyers out there but the person I reached out to was exceedingly thorough in explaining things (and I, as a dev, had lots of rules-lawyery questions to throw at them), quite prompt in their response and charged a modest fee.
Speaking to a lawyer will absolutely cost you more than a coffee, but it's not that pricey in the scheme of things compared to getting in legal hot water.
Without a writ, you have little idea what the substance of their legal claim is; there's no purpose in hiring an attorney, because there's nothing for him to work on. So you are saying: "I don't fold to hollow threats and bullying. If you have a proper legal claim, make a proper legal claim."
If you then get a writ, show it to a lawyer.
If you have no substantial assets, it might be worth pointing that out (once the writ arrives). Nobody wants to sue a man of straw.
I do agree with those who say get a lawyer to send your response. However you should still do the research yourself - to the best of your ability. You can save yourself some expensive lawyer time by knowing the basics and having a potential draft (be careful: make it clear that you do not have any emotional ties to it so the lawyer is free to tear it up) of your response.
