That's a lovely story about Staines. Thanks for sharing it.
I think the Packhorse is still there but now has a much more complicated name, the "Mercure London Staines-upon-Thames Hotel" (!)
(Staines changed its name to Staines-upon-Thames back in 2012 but of course everyone still calls it "Staines".)
I'll have a look for the Packhorse/Mercure the next time I'm in the town.
The pub I know best in Staines is The Bells in Church St. It's very friendly and does very good food.
I wonder if you remember that one at all?
If the Packhorse is where I think it is, The Bells is just a short walk round the corner towards St Mary's Church and the park.