Is it definitely not earthed via the steelwork or some other natural connection? Perhaps even between the rebar and the strut embedded in the concrete?

Indeed, is there rebar in the concrete floor and is that adequately earthed?

Completely floating is unlikely to meet the needs of ENA TS 41-24 or BS EN 50522, unless there's a specific reason for it. I can't think what the advantage would be to having the tray floating and looks like bonding would be very easy to achieve, but I would be inclined to contact the designer, or at least their specification in case there's something we're not aware of.

Of course conformity to a standard and risk assessment aren't the same thing. I'd not want to do the latter on the basis of this much information.

Is it definitely not earthed via the steelwork or some other natural connection? Perhaps even between the rebar and the strut embedded in the concrete?

Indeed, is there rebar in the concrete floor and is that adequately earthed?

Completely floating is unlikely to meet the needs of ENA TS 41-24 or BS EN 50522, unless there's a specific reason for it. I can't think what the advantage would be to having the tray floating and looks like bonding would be very easy to achieve, but I would be inclined to contact the designer, or at least their specification in case there's something we're not aware of.

Of course conformity to a standard and risk assessment aren't the same thing. I'd not want to do the latter on the basis of this much information.