OS Map with custom markers

I need a UK OS Map based on this example: https://labs.os.uk/public/os-data-hub-examples/os-maps-api/zxy-27700-basic-map with custom markers using data supplied in a text file, each marker to have a pop up containing location data and a URL.

*edit*
Following feedback in proposals, here is some more info...
I did have this working on a previous version of OS mapping, but this has stopped working and the api is being phased out. I prepared a text file on demand which was referenced by the html file and plotted the markers on the map. The text file consisted of lines like this:
542600,326100,site,Current Site: 1067 Sample Airfield [L-]Grid Ref.: TF426261 (542600-326100)Type: PowerWind dir.: 000-359 Resident Club: Sample No. of Users: 2

The initial values determined the point on the map where the marker was placed, the 'site' determines the type of marker displayed, and everything else is what appears in the pop-up.

I can supply the text file in whatever format is needed for the new OS api.