Neither the Home Office or the police have any involvement in civilian range design/certification/approval.
As far as using firearms held on an FAC for target shooting, you only need to adhear to the conditions on the certificate. ie. Suitably constructed range and adequate financial provision. The former, there are no formal requirements. The latter is being able to obtain insurance.
In the case of Home Office approved clubs, the club inspections are done by the police. Which could be where the confusion starts.
But all the police are doing is checking that all the club procedures and record keeping is in place. If they visit the range it is only because that is where the club meet. Though it is usual for them to take an interest in the facilities that shooters are using, but they have no say in that side of things.
Tube ranges are a very convenient way of making a NDA (non danger area) range.
Any construction that provides the material thickness' required for the calibre, is fine. Pre-cast concrete tubes are good, but heavy and expensive.
I was involved with one built from a concrete base, 4" dense concrete walls either side, and capped with 2" solid concrete slabs. That was overkill spec for rimfire.
The backstop was steel plate with a rubber curtain. And though this would have been fine as a bullet catcher, we decided to try a rubber chip catcher, leaving the plate just to catch flyers.
Anyone looking at buller catchers, I cannot recommend rubber chip enough.