Put all 80k savings into ISAs or split some among high interest savings accounts?

[JohnnyBee]

We have about 80k in savings and save about 2k a month. We're mortgage free but need to spend 60-70k on a kitchen extension probably next year when brexit nonsense might be a bit clearer.
Also may need to do a loft extension in next few years which will be 60k.
We have put about 40k in cash isas fixed for 1 year at 1.75%.
Any thoughts on where to save the remaining 40k plus the 25k we should save over the next 12 months?
There's obviously lots of banks offering attractive rates for opening new a/c's but it's just for a few thousand?
Is it worth the hassle of doing that or do I take the simpler option and stick it all in an ISA?
We are quite risk averse so don't want to do anything where we could lose our money.
Any thoughts appreciated?

I’ve got that sum in premium bonds. Risk free. Pretty much instant access. Decent win rate equivalent to interest rates.

www.moneysavingexpert.com/savings/premium-bonds-calculator/
This suggests a win rate of 1%

That’s a bit more than I get in the bank for instant access.

Would it be cheaper to move?

Premium bonds are a terrible win rate. God knows why people keep suggesting them on threads.

You can get 1.5% instant access still with a Marcus or 2% on a 1 year fix eg with ICICI. More if you fix for longer.

I couldn’t be bothered opening lots of accounts just to stick 2/3k or dripping monthly payments into the regular saver account for the bonus interest rates. You hassle to profit ratio may be more tolerant than mine.

Atom fixed saver?