Amount to go into a fixed term bond

[firemunki]

I think this is probably a relatively simple question but other opinions are always welcome. It's not powerfully built director levels of investing but still not inconsequential to me.

I've got an NS&I ISA that's around 1.7% with ~15k in it and want to get it working better for me. I'm thinking about a 1-year fixed-term bond but unsure of the amount to put in. Planning for a year only as the 2-year and 3-year options were only slightly higher interest. Plus the way things are going I don't want it to be locked out for 3 years and then have a jump in rates.

• £10k now which leaves me with approximately 3 month's salary as an emergency fund to rebuild and then reinvest again in 12 months' time.

• £6k or 7k now and then wait 6 months and set up another 1-year bond for another £5k or 6k.

The larger amount would be easier to set up but would leave me with a smaller emergency fund ( but I could get money after a short period from a Stocks and Shares ISA if needed for an emergency). The 2nd option would allow for the emergency fund to rebuild and could put more in each time individually as there are still plenty of emergency funds left. The second one doesn't need to be as much if life stops me from saving quite so much.

It's probably much of a muchness here with neither option much better than the other but I would like some outside opinions.

[MaxFromage]

You can get fixed rate ISAs that allow withdrawals with just a loss of interest. Virgin 2 year ISA for example, at 4.11% 90 day loss of interest if you have to make a withdrawal.