🚀 go-pugleaf

> Having determined that [my Sperry PC] has a primary release version BIOS ROM
> (1.34F) and that later versions supposedly fixed the stupid bugs
> which are plagueing me now, I've been trying to contact their
> spares/customer support dept. 

The only phone numbers I have are toll-free (800 prefix numbers) valid only in
the USA.  I do have some information for you:  the correct Sperry part number
for the latest BIOS chip set (version number) depends on which version of
motherboard you have.  I am assuming you actually have the Mitsubishi-built
machine since the BIOS number you gave was one of their early ones.  
First you need to know whether you have what they marketed as the HT (big ugly
metal box), IT (much smaller), or micro IT (definitely small foot print).  

Next, for the HT at least, there are different levels of motherboard, each of
which takes different BIOS chips although they have essentially the same BIOS
code.  Motherboard numbers for the HT include WESY1 [has a little stick-up
add-on near the powersupply, 128K], WESY 10 [128K without that doodad], WESY30
or 31 [256K, floppy controller on the motherboard], etc.  The respective Sperry
part numbers for these for the ver 4.71 Mitsibushi BIOS chip set would be 
F5083-00, F5083-01, F5083-02, each one slightly different and matching specific
WESY #'s only.  Unisys has essentially stopped selling directly and these
upgrades are handled by sales in the USA, not by service, so try finding their
UK distributor and/or a dealer.  For your bargaining info, Unisys's price to 
their distributors is about $30, distributor to dealer about $45, and the
retail list is about $100.  Incidentally, if you are using Hercules graphics 
cards or clones, the new BIOS chips introduce all sorts of new video 
incompatibilities, but they're fine otherwise, especially re. hard disks, 
COM problems, etc.  The latest DOS release for these machines (3.2) also helps 
fix some of the annoying incompatibilities and you can buy the DOS/BIOS combo 
as a set under its own part number for about 50% more.   
I recently upgraded 8 of these machines and it was worth doing except for the
Hercules problems.