Norwegian compensation claim no notice cancellation

Nick_V

My flight 5 July 2022 LGW to Oslo 09.20 was cancelled with no prior notice despite their having my mobile for SMS updates.No reason or apology given.  I filed a compensation claim via their website for £440 (2 PAX) on 5 August with all relevant information. Nothing since other than limp excuse of overwhelmed by volume of claims, despite calls, emails and letter threatening legal action. Norwegian are not part of any ADR scheme so that route seems unavailable and since the liquidation of their UK subsidiary, they don't appear to have an address for service of legal documents in the UK so Small Claims Court not applicable either. Any ideas? Thanks