How do I deal with advance funding for SMP I've received funding for an employee on maternity pay but it shows on my profit and loss as takings.

This should be shown on your balance sheet as a liability until claimed.  You can journal across.

Dr.  ( Account where it was entered)

Cr. Current Liabilities - SMP Advance funding

Once the SMP is claimed then you would put through an appropriate jnl

Dr Current Liabilities - SMP Advance Funding

Cr P & L Account ( Smp received - payroll costs)