How to pay tax and nic

A client, british citizen, is returning to UK after 5 years working full time for a Foreign employer. He will continue to work for same employer on same contract which provides for hourly rates in euro's plus daily subsistence. He is paid in euro's by transfer to a UK bank account. The client is aware that the employer now has a UK base and is employing UK people on UK contracts and presumably operating PAYE.

He wants to get his UK tax position sorted and pay over tax and nic on a regular basis as an employee. Will he be taxed as an employee of the UK employer and what rates of subsistence can be claimed as tax free, if any? Can anyone help with the mechanics please if he has to pay by direct collection.