This is a bonus cache of an Adventure Lab! To obtain the coordinates, you will have to play Avon Venture: Part XI - The Streets of Bexley. Expect about a 2.5km flat walk or bicycle ride to complete it. It is also possible to drive and park within 200m of each location.
Have a read on the listing page of GC9YTT8 - I & II Bonus Cache for general information on this series.
If you haven't played the previous parts, I would recommend going back and doing those:
Avon Venture: Part I - The humble beginnings: adventurelab.page.link/dNNo | GC9YTT8
Avon Venture: Part II - Ōtākaro: adventurelab.page.link/z7Pd | GC9YTT8
Avon Venture: Part III - Ōtākaro: adventurelab.page.link/QpiU | GC9Z2DP
Avon Venture: Part IV - Ōtākaro: adventurelab.page.link/BBwt | GCA013V
Avon Venture: Part V - A Hospital Pass: adventurelab.page.link/fTxf | GCA0D7P
Avon Venture: Part VI - Manchester to Barbadoes: adventurelab.page.link/unui
Avon Venture: Part VII - Oranga Hōu: adventurelab.page.link/nMzp | GCA0CF9
Avon Venture: Part VIII - The Red Zone: adventurelab.page.link/SgNn | GCA0055
Avon Venture: Part IX - Ōtākaro - Red Zone: adventurelab.page.link/XMN5 | GCA1A4R
Avon Venture: Part X - Burwood to Bower: adventurelab.page.link/PpqB | GCA3WJF