Like you I am currently RTITB certified but joined iTRUK as well so I could train people to operate safely but to a work standard rather than "test standard".
You could consider using plastic pipe to create the barriers. Would need the fittings to hold them upright and then horizontal and could have it high enough so that it moves if touched by the truck. Means an initial outlay but its waterproof and easy to move.
Good luck with the training.

Aye the casks for us are just spaced out and I have put them a critical turning points to give them the feel that they need to be looking around at all turns but its not the same, it is pretty easy still to get through.

I am currently RTITB but can't see us ever moving.. but in my earlier years starting out i worked up north and there are that many sites to cover we would usually get away with using pallets if the site actually had any decent flat ground, but this was rare. So we just had to adapt as best as we could. Now though being based at 2 sites and bringing them to the one site for their novice I just feel we can do better.

There is only one place on site they use industrial racking and its for one small group on site, the majority will be moving a skip, pallets or IBC's outdoors.

I had considered using empty IBC's to create the barrier for the chicane but the fact they will be picking up IBC's during the training i just felt they would be swimming in a constant IBC's.

I train both, and quite regularly. Though with the refresher for the guys at the warehouse that just move casks I tend to keep them on site demonstrating their ability to safely handle casks in different scenarios as they are always working in outdoor open spaces, but now also including the driving in and out of warehouses with the new FLT's we got on site recently that are aimed just to minimise the manual handling aspect with the long warehouses (been there and don't miss it). Otherwise some refreshers i will just get along to the static training course and cover them there.

Hi Shaun
Think we must work in the same industry as my predecessor did a similar thing.
Like you I did not feel comfortable with using casks as they are pain to line up properly.
I have used the barriers you mention, they are okay as long as the wind isn't blowing a hoolie if you have the feet in line with the barrier.
I have managed to get round the issue of using the chicane by joining the new kids on the block (iTRUK) as they have effectively done away with the chicane and operating the truck to the test written in the 1960's.
Are you using Industrial Racking at any point in the training or is it purely outdoor training?
Do you have any empty IBC's or stillages you can use if you need to create a barrier?
Are you training novices or experienced operatives?