Digital Nomad Visa - employers liabilities

I am employed as a remote worker for a UK based company and I am paid via PAYE. I wish to apply for a digital nomad visa to work from Greece. My employer has rejected this request stating that they have been advised that 1) this poses a tax risk to the company and would require them to establish an international payroll. 2) The employee would also need to be removed from the PMI scheme and there are implications around the Group Income protection scheme and finally 3) There is also a risk that the employee is subject to local employment regulations due to the time spent in the country, working under Greek regulations. I have been informed by a lawyer and accountant in Greece that this advice is incorrect. There is no double taxation rules for Greece but my employers are not satisfied and I am trying to secure confirmation for them that this arrangement remains in place with Greece following Brexit and that there will be no financial implications for the year which this visa runs. How can I secure this confirmation please?

Hi,
You can find the tax treaty between the UK and Greece at 1953 Greece/UK Double Taxation Convention.  
There is no agreement for tax purposes on employment income or other income in the agreement.  
Further information may be found at DT8250PP - Double Taxation Relief Manual: Guidance by country: Greece:.
Thank you.