Going back to your tubing idea...
The pins which fit into the Molex Mini-Fit Jr. "receptacle" housings are actually tube-like. I don't know if they'll fit snugly over the pins on your adapter, or not, but they're not terribly expensive--couple bucks per 100 (or about a pound). The shipping will cost you more.
In the US, one would shop at Mouser or Digi-Key, but I'm not sure who are the good electronic supply mail order houses in the UK. Still, Digi-Key's web site is well organized. You may wish to look up the Molex Mini-Fit Jr. line of housings. Then look on that catalog page to identify the corresponding pins for the receptacles. That'll give you part numbers. You can also probably find a mechanical drawing of the pins there which will give you dimensions.
Then you can try crimping wires onto the pins, and soldering them after crimping, if you wish. Connect the other ends of the wires to a DB-25 connector perhaps. Then when it is all done, simply slide the Molex pins over the appropriate adapter pins, and that way you needn't do any soldering on your adapter.
The odd thing about the Mini-Fit Jr. housings, is that the ones that look like plugs are called receptacles and vice versa. The reason for this is that the pins which install in the plugs are male and the pins which install in the receptacles are female. So even though the large plastic plug housing looks female, the pins inside are male and vice versa. Hence the odd naming convention.
Also, if the Mini-Fit Jr. pins are not a good fit, I'd look for some other crimp on pins which do have the proper dimensions. One of these two part numbers, WM2312CT-ND
WM2513-ND, is tubular, crimp-on pin with a smaller size than the Mini-Fit Jr. pins. The other is a springing action pin, so you'd need to look at specs to pick the right one. Or order both. Again, they're cheap. And don't forget to order a DB25 housing and pins while you're at it.
The pins which fit into the Molex Mini-Fit Jr. "receptacle" housings are actually tube-like. I don't know if they'll fit snugly over the pins on your adapter, or not, but they're not terribly expensive--couple bucks per 100 (or about a pound). The shipping will cost you more.
In the US, one would shop at Mouser or Digi-Key, but I'm not sure who are the good electronic supply mail order houses in the UK. Still, Digi-Key's web site is well organized. You may wish to look up the Molex Mini-Fit Jr. line of housings. Then look on that catalog page to identify the corresponding pins for the receptacles. That'll give you part numbers. You can also probably find a mechanical drawing of the pins there which will give you dimensions.
Then you can try crimping wires onto the pins, and soldering them after crimping, if you wish. Connect the other ends of the wires to a DB-25 connector perhaps. Then when it is all done, simply slide the Molex pins over the appropriate adapter pins, and that way you needn't do any soldering on your adapter.
The odd thing about the Mini-Fit Jr. housings, is that the ones that look like plugs are called receptacles and vice versa. The reason for this is that the pins which install in the plugs are male and the pins which install in the receptacles are female. So even though the large plastic plug housing looks female, the pins inside are male and vice versa. Hence the odd naming convention.
Also, if the Mini-Fit Jr. pins are not a good fit, I'd look for some other crimp on pins which do have the proper dimensions. One of these two part numbers, WM2312CT-ND
WM2513-ND, is tubular, crimp-on pin with a smaller size than the Mini-Fit Jr. pins. The other is a springing action pin, so you'd need to look at specs to pick the right one. Or order both. Again, they're cheap. And don't forget to order a DB25 housing and pins while you're at it.