Find the Latitude and Longitude for your Conference Meeting Place
Get the full postcode for your meeting place, for example from your parish priest.
Log on to the web page
http://www.streetmap.co.uk/gridconvert.html
Here is a sample of entering a postcode on the web page

Click on the Post Code button and then the Convert button.
Here is a sample of the results.

The numbers you want are in brackets on the right column in the Lat and Long lines.
In this case Latitude 55.666449 and Longitude -4.270433
If you want to check that the result makes sense then click on the
"Click here to see location".
You get a street map and if you scroll down then the result is shown by
a big arrow.