T3, 3-dr. hatchback - w/screen washer bottle leak

[Man @ 48]

Symptom: when filling/adding water to reservoir it just pours out from under the car.

This has happened twice recently; I haven't used the car much and the first time was a couple of days before the MOT. The tester said that 'the hose' had come adrift and that he'd 're-fixed' it. It has just happened again but before I take it back to the workshop (which has to date been fair and trustworthy) I was hoping if somebody here could explain which hose(es) might be involved and if a method exists (eg. jubilee clip) that will permanently solve the problem. I'm approaching 70 so well past the time when I stopped getting under cars!

Many thanks.

Bill