The place in question is Ma Tau Wai Service Reservoir Playground, which most birders here just call Ho Man Tin.
The easiest way to get there is to reach Sheung Wo Street (a couple of minibus routes have that as a terminus), then walk along the road that goes up.
There are other smaller parks in the vicinity that sometimes attract migrants (King's Park, or indeed the East Service Reservoir Playground that you mentioned), but they pale in comparison to Ma Tau Wai.
[ Last edited by bittern at 4/10/2022 14:25 ]