Thanks Mac t K
Thanks for that generous offer Mac t K, but I've ordered a couple of these adapters to see how they go.
But I did open a can of worms with my query. The Misco link to the D-Link DE-855 didn't work or, to be more precise, took me eventually to the exact product but now marketed by Dynamode as the TT-T2. I've ordered two of these at £33.99 +VAT from Insight (ex Action). Other suppliers would charge up to £45 odd +VAT.
There is one other product made by Allied Telesyn at a similar price but an entirely different item.
That's it. These 10Base2 to UNC Media Converters are as rare as hen's teeth.
Thanks to tho others who contributed to this. My building has 12 connection points in 5 rooms on two levels. AEsthetics takes priority over saving a penny here and a penny there. I can have no exposed wires or trunking. So extended UTP to a hub can't be a contender. So these Media Converters are the best compromise. I'll try the Allied Telesyn items eventually and report back in case anyone is intrested.