... I'd be interested is hearing from anyone who has changed from First Direct to another bank
I am one of those people.
My first bank account was a Lloyds TSB Young Saver account when I was 17. It used to pay a reasonable amount of interest, if I recall correctly.
When I got an iPhone 3 GS in 2009, I looked for mobile phone insurance and opted to upgrade my old Lloyds TSB account to a Lloyds TSB Silver account, to benefit from the cheap mobile phone insurance (that I used several times to get a new/refurb phone - £30 excess each time) and AA cover (that I also used several times).
A few years later I switched to First Direct as they were offering a £100 bonus (and still do) and (at the time) an 8% Regular Saver account.
Several years after that, I started doing lots of transatlantic travel and heard about the Halifax Clarity card. I applied for the card and whilst I did that, I saw that Halifax was offering £100 to switch bank, so I switched.
Even if you move your everyday banking to another bank, it's sometimes still worth keeping your old accounts open:
* First Direct 1st Account - gives me access to the First Direct 6% Regular Saver (I had several 8% Regular Saver accounts before First Direct reduced the interest rate)
* Lloyds TSB Gold Account - gives me access to subsidized/cheap perks like mobile phone insurance, worldwide travel insurance, AA cover
* Halifax Reward Current Account - gives me access to the £5 /month reward