I am asking for help and advice on where to go - which regulator I can file a complaint against this scam exchanger
I never heard about this exchange, but you should not hold coins on any exchange, unless you want to take high risk and give control of your coins to third party.
Coingecko does not have available listing for this crap exchange, and coinmarketcap is showing this as unlisted:
Launched on 01-09-2017, is a centralized exchange located at Suite 11 Penhurst House, 352-356 Battersea Park Road, London / UK. It supports GBP, USD, EUR, RUP and JPY fiat deposits with all bank cards.
https://coinmarketcap.com/exchanges/n-exchange/