They want the original will - I only have one copy and surely Probate will need that
Yes probate need the will - but why do the ISA people need the will? Are you working ahead of getting probate and closing investments now?
You need to get probate sorted first, which only needs approx valuations, then you send the probate certificates off to all financial institutions to close/transfer accounts. This is what I did when my mum died 4 yrs ago, I found it very straightforward, but didn’t attempt to get any money before probate.
Is there property, and is it being passed to children/grandchildren? If so, I think the IHT limit becomes 500k (325 basic, plus 175 for house) per person, so a million in total?
www.gov.uk/inheritance-tax/passing-on-home
You can set up an executor account to pay the cheque into, or ask the paying company if they will pay direct to yourself. I used a second bank account that I had, and just needed my brother to sign to authorise mums bank proceeds to go into it, then I transferred half out to him. The house sale proceeds were sent directly to each of us by conveyancing solicitor.
My DB dealt with utilities and got a refund quite a while after her death, paid to ‘executor...’ he just rang them and asked them to pay to him directly, then sent me half.