HIfi-remote.com has an upgrade file for the Eltax HT-154.  It uses the  NEC1 IR protocol, device 0.191.

You're in the UK, right?  Then a OneForAll URC-7950 has a setup code that you can customize to work, assuming the 153 responds to the same IR signals as the 154. The URC-7940,  7960, 7525, 7780, 7781, or 8350 would also work.  OneForAll may also have some newer models that will work.

The remote will need customization, which you would do by entering a 5 digit EFC for each function.  If you decide to go this route, we can tell you the 5 digit numbers.