By Huw Jones LONDON (Reuters) – Regulators in Ireland, Luxembourg and the Netherlands allowed investment funds shifting operations from London to the European Union after Brexit to operate with too few senior staff in their new locations, the EU’s securities watchdog said on Thursday. After Britain voted in 2016 to leave the EU, hundreds of investment funds, trading platforms, banks and insurers raced to open hubs in the EU as they would no longer be able to use London as a base to serve the EU from the end of 2020. The European Securities and Markets Authority (ESMA) set out guidance to stop …