We host weddings, parties etc in one of our premises and, in the course of the evening, we clear tables and put empty bottles in what are basically wheeled open containers. 

The next morning containers are taken to our recycle point for emptying - which leads to employees leaning over into bins causing back strain.

I would like to purchase containers with a rise and fall facility that will bring bottles to the top as the container is emptied.

I've tried a number of web searches but no joy - would anyone know where I could source this type of container?   

Take it you are referring to items similar to those on this web site (no affiliation)

https://www.bin-shop.co.uk/bottle-bins

I would talk to your waste service many of the venues and busier restaraunts near Chez Roundtuit use the bigger wheelie bins which the carrier lifts and tips with their collection vehicle

It would be difficult to locate a commercial solution in which the base of the bin moves up and down dependent upon the weight within - you also have the problem of how to keep such a container clean given liquids will accumulate underneath