I built two shower enclosures and both eventually leaked, then 10 yrs ago my wife saw one of these at the range, we bought one and it's been just superb. I paid about £100 extra for the steam generator type but no-one ever uses it now (the steam). It's just a bloody good shower.
I have a self contained freestanding shower cubicle. Came from a local company for £150 but brand new cancelled order that cost nearly £1000. I can always ask if they still have any for sale (they had five). https://taplanes.co.uk/products/view/6/alpha-cubicle
Small update on this. I spoke to the seller a week or so ago and they confirmed it's a concrete floor. Not ideal so may have to look in to other options for getting services there if I decide to go ahead with it