It's definitely a maple and given the frequency/prominence of the sycamore maple in the UK and the leaf size and shape, that is a reasonable guess.

The bark is also a match

Just to put things together: Acer pseudoplatanus (commonly known in the UK as Sycamore )

Yes. Extremely common in the British Isles, to the point of being a weed species in small urban gardens where it self sows merrily along with Ash.

Your council is not helpful. The tree has a number tag so they must have a record of it. What’s their problem? I’ve enquired about trees to other councils and they’ve been very helpful.

Do you know about this group? Looks like the involved public agencies - including the one Council - aren't the only interested parties. Maybe you can find out more about the plantings from them.

http://www.ashtongardens.org.uk/about.htm

>What's their problem?<

From the page linked to above (read between the lines):

Through public subscription we funded a leading charity law barristers opinion to show that the Gardens were a charitable gift held in trust for the people of the town. The Charities Commission has written to the Council to remind them of the need to register and regard the gardens as a charitable trust.

We opposed the planning applications that would damage the cultural and historic integrity of the Gardens

Our members worked with the Garden History Society and English Heritage to have the Gardens listed.

We successfully lobbied for the refusal of the first Safeway plan to turn part of the gardens into a car park