Group savings account - any ideas??

Dear Money Saving Experts,
I am after some advice!

Myself and 3 of my friends turn 40 in 5 years time, and have decided to set up a group savings account to save towards a lovely holiday to celebrate this occasion.

We all have ISAs already, and we don't have a lump sum to deposit as an initial account opener.

So, I have been looking at a regular savings account, but, all the high interest rate ones seem to be only available for approximately 12 months.

Is there another type of savings account I could look into? We would not be touching this money until we needed it in 5 years time, and would be making fixed payments each month.

I am not particularly financially savvy, so any ideas would be greatly appreciated with regards to this.
Thank you!