I know you're not interested any longer, but someone else who reads this may be ...

From the government planning portal:

"You will need to apply for planning permission if you wish to erect or add to a fence, wall or gate and:
it would be over 1 metre high and next to a highway used by vehicles (or the footpath of such a highway); or over 2 metres high elsewhere .....

You will not need to apply for planning permission to take down a fence, wall,or gate, or to alter, maintain or improve an existing fence, wall or gate (no matter how high) if you don't increase its height"

So in theory you could have maintained it at its original height, since you were going to "maintain or improve" it. (Subtleties like this aren't always uppermost in the minds of council officials). Since this was the fence between you and your neighbours, I'm not sure why they were applying the lower limit.