The Omega B was designed in the late 80's/early 90's so i think it would be pretty fooked too, a bit better yes.. A V70 would probably fare better but I think the Modus still could be OK, "modern" small cars are generally very safe and strong.
Omega B are not late '80s design, but early seventies; the structure is barely changed from the Carlton when strong and rigid were the main requirements. Modern thinking intends that the energy from an impact is absorbed by as much of the car as possible, while the occupants are protected by active measures like multiple airbags. This is what makes a recent small car 'better' to crash than an old one. Although a well designed large car will be even better at absorbing the crash because there is more material and space to do so.
The real limit here is not the car(a Smart is really strong for instance)but the pink squishy things inside it.