Hi,
I live on the opposite side of the globe, I don't know a good UK supplier.
If you are serious about updating you need to decide on an external motion controller, that will determine future development options.
All I know about your machine is that it has a parallel port. Does it have one or two? If it has one then you have 12 outputs and 5 inputs.
If you want/need more you will require a controller with more IO than the equivalent of one port.
Lets assume that you have one port and that is all you require. There are three devices that would be of interest to you, the UC100, the PMDX-411
and the 57CNCd25. All three are good and are very similar to one another. They connect to your PC by USB and have a DB25 socket as output mimicing
one parallel port. You might call them a USB to parallel converter but they have an FPGA inside them which makes them way WAY too clever to be
a converter, they are genuine external motion controllers.
https://www.poscope.com/product/pokeys57cncd25/http://cncdrive.com/UC100.htmlhttps://www.pmdx.com/PMDX-411These can be had for about $100 to $120. Beware the Chinese are making UC100 rip-offs and selling them cheap on EBay and Amazon, they don't
work like the real thing. Buy direct from the manufacturer or their nominated distributor or you will get ripped-off every time.
If you want more IO then you need to look at:
https://cncdrive.com/UC300.htmlhttps://warp9td.com/ The ESS is the model of choice
https://www.poscope.com/product/pokeys57cnc/These three devices have plugins for both Mach3 and Mach4. The UC300, the ESS and the 57CNC have 85, 51 and 57 inputs/output respectively. The UC300
and the 57CNC have some analogue inputs as well for extra flexibility.
http://www.pmdx.com/PMDX-424 Is a good two equiv port (31 inputs/outputs) offering by PMDX but is Mach4 only.
Warp9 Tech Design and PMDX are US companies, CNCDrive is Hungarian and I think PoKeys is UK based.
Thre are a couple of other choices, Vital SyStems (US) HiCon and CSLabs (Poland) CSMIO but they are expensive and I wouldn't recommend the CSMIO for Mach4.
The HiCon is about $600US but very VERY capable, price not withstanding, it is worthy of consideration.
http://www.vitalsystem.com/portal/motion/hicon/hicon_integra/hicon_integra.phpI haven't bothered with any of the cheap Chinese, or even the not so cheap Chinese stuff.
My recommendation is to do some research on these units, decide on one. You could still run your existing copy of Mach3 even on your original PC. Those
could be updated later at your convenience. You will love the wide range of PC's and OS's that will now be very effective PC platforms for Mach. If you choose
from those I've mentioned you could update to Mach4 at a later date.
Craig