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Still confused, as MoneySavingExpert.com (who are usually spot-on) say
"Transferring an ISA allowance is a technical process, not just like switching a normal savings account. Yet as long as you abide by the golden ISA transfers rule, it should go smoothly.
"Never, ever, ever, ever withdraw money from a cash ISA!
You'll immediately lose all the tax benefits."
Instead speak to the new provider and fill out a transfer form. This will usually include a note you can send to your existing ISA company. Your new company should then sort it all out, including moving the money over for you, keeping your tax benefits intact. "
So if after a while I want to (for example) take all my ISA money out to put towards a new house, I WON'T lose out? (I'm only talking about cash ISAs here.)
Thanks for your answers so far, folks