I've often wondered at what size the rooms at the top would be in these buildings.
They don't look as if they have much headroom in them.
Anyone lived in similar?

I can put you out of your misery Derek! I had mates who lived on the corner of Brandon Street at No 29 Hamilton Square. The very top floor flats are just like a modern flat with 'normal' head room. A mate at work got the top floor through another mate who had a flat on the floor below (2nd floor). This floor was slightly more spacious and had head room more like a Victorian terrace house with Dado rail, picture rail, and high-ish ceilings. They were both cracking flats having the Town Hall on one side and the Square on the other.

Usually servants' quarters. When these were built, even a family with a quite modest income would have a couple of servants.
When you consider how labour intensive housekeeping was in, say, late Victorian times and how the mistress of the house spent most of her time pregnant, the need for servants was clear.

A good way to find out is to search the Wirral council planning portal.

Stick in the address / postcode and see if there are any old plans.

I found some for some work done at 12-14A Grange Mount, back in 2000.