Hi Gary,
Not really answering your question i'm afraid but FWIW:
I spoke with Direct Water Tanks whose price was jaw dropping, especially given it was a standard rectangular tank - no fancy cut-outs or shapes. £660 + VAT for a 900 x 700 x 200. Don't get me wrong I understand the cost of bespoke manufacture, but its a lot of money compared to off the shelf tanks.
I went with an AF Tank from Marine Scene in the end. I only ordered it a few days ago and it hasn't turned up yet but can report back if you're interested.
I was going to push the button with a CAK tank but they get REALLY bad reviews on google re. delivery/ customer service, and didn't respond to my e-mail asking for a quote so for me they are not worth the potential hassle. Use with caution.