How are you going to demonstrate the operator competently errected the tower if an accident occurs?

PASMA certification is a requirement for use at our site  https://pasma.co.uk/training/

yes it is work equipment...you need training...don't think you need external so long as you can demonstrate that you have trained everyone in the use using the manufacturers instructions...

Hi, can we have one trained and the others can then use it?

JHF - suitable training doesn't necessarily equate to needing a certificate, though it might be a requirement of your systems or if being used for someone else, such as a client where you are their contractor.

I hate to come up with the ubiquitous answer but it does depend on your risk assessment!

You might decide in your risk assessment that one person erects and attaches a "scafftag" [NOT a legal requirement under UK legislation] to say that it's safe [perhaps with an indication of any constraints e.g. maximum load] and then perhaps all the training the users need is some instruction to use the internal access and not to alter the tower in any way.

If it's a mobile tower, you might also need to tell the users that they must lock the wheels/castors each time they have moved it. Whether that counts as instruction or training is somewhat immaterial.