Fitting a Marino double bath - gaps at end, what to do?

Hi hoping for a bit of advice.

I have a double marino bath as in the picture.

Plumbing is not a concern however the bath frame, tiling and finishing the end gaps (140mm) are a challenge.

In particular im assuming it would be better to build frame, install bath, use a tile tray at far end bath edge but as for the gaps i have no real idea how to attack this.

If anybody has any suggestions i would be very grateful for some advice.

Assuming no jets or pumps:

Believe me, with the tub in its present position plumbing could be a future difficulty if any plumbing repairs are needed, and your plumbing is inaccessible.
Think about building in a tub that could be easily removed ie. the supplies being accessible for isolation and disconnection, and the waste similar.

Or better still, swing your bath around to place the taps on the outside.

You could build a 50mm x 50mm frame for the c/w bath panel, and return frames at each end for your "tile tray"
Vertical, tiled 140mm panels could be used at either end of the bath panel.
Use backer board for the "tile trays" & tiled panels.

Its also possible to build a removable tiled in bath panel.

Do you intend to have a separate shower?

This issue has been covered before in the forums - perhaps research it?