You can combine the two, but you might not want to.
The advantage of your workplace pension is that your employer pays in to it (and you can choose to do so, or not).
The advantage of your other pension is it's not tied to a job. (I have a similar amount in a stakeholder pension I stopped paying in to a decade ago, but its performance is ok so happy to leave it there). So it will always be there.
If you change job, then you get a new pension through new employer, and you end up with 3 different pension pots. At some point it may be worth consolidating them, but if they are all low-value then actually the fees to transfer the monies might be too high to be worth it.
If you want to move your other pension then don't assume your workplace pension is the best option - it might be more convenient, but might end up costing you money if its performance is worse. And there will probably be a fee for moving your money.
Both providers should give you annual updates on performance, investment risk, value - so you can compare and see whether you think you would be better off moving.
If you do want to move your old pension into your workplace pension, you'll need to speak to your workplace pension provider to find out if it's possible.
If you don't, you can shop around and see whether there's another better home for your old pension, and just transfer it.
42 is a good age to be making proper retirement plans - if you leave it much longer, retirement will be approaching very rapidly. Personally (at 39) I am not willing to rely on the state pension still having any value at all in 25+ years' time.