George, the AsanteTalk is still listed on the
Asante Web site. It is available new for $78 from the Asante store. I purchased a refurbished AsanteTalk directly from Asante for around $50 a few years ago. If you contact Asante they may be able to direct you to a U.K. reseller. eBay USA has three AsanteTalk listings as of this writing so you might find something on your eBay...
Your LaserWriter is AsanteTalk compatible according to this
compatibility chart.
My LaserWriter is connected to an Apple Extreme Base Station and is available wirelessly to any Mac connected to the LAN. I am still hoping to someday get my full $1350 investment out of that printer!!! (At the rate I print that should be around 2025...)
One thing you should know if you wind up getting an AsanteTalk is that the connection is dropped whenever power is interrupted to the adapter. Resetting the AsanteTalk by unplugging it from its power supply gets it working again... It takes around ten seconds for the printer driver to recognize the printer when you attempt to print again after resetting the AsanteTalk, so give it a little time before fiddling with the AsanteTalk some more.
I think that Farallon also made a similar Ethernet adapter, but I have been unable to locate its Web site.
The Fixyourownprinter forum should be your next step; the info on the Web site itself is rather limited.