Pension contribution limit uk resident, income from multiple countries

I am UK domiciled and UK resident. I am a cross boarder worker who earns money in the Republic of Ireland and Northern Ireland. I file self assessment in the Uk and declare both incomes. I want to make a big contribution to my SIPP this year. What is considered UK relevant earnings for this purpose? If I made €20,000 working for an employer in Ireland and £20,000 working for an employer in the UK what is the maximum amount I can contribute to my SIPP? I owe a balance of tax to the UK on my Irish earnings due to the personal allowance applied to my Irish earnings (I am a non resident in Ireland for tax purposes) Does this effect the SIPP contribution cap?

Hi
It is the total you earn so for this scenario it is £40k and is not affected by any outstanding tax due.