I'm approaching my birthday and plan to draw down my 25% tax fee lump sum from my Vanguard SIPP.

What are the mechanics of this with regards to reporting via Self Assessment?

I don't need the money but I want to get it out of the pension and into ISAs whilst I have the chance / available allowances.

I don't plan on drawing any other funds from the pot for some years.

Are their any issues I ought to be aware of??