Brilliant - thank you very much.
I can confirm that TestComplete seems to work just fine with the svn.exe supplied with Tortoise.
It does NOT need the one specified in Help Page. Indeed, Tortoise is ALL you need and T/C will find the path all by itself.
The reason that I didn't have the utility on my PC is that the command line tools are disabled (by default) in the Tortoise Installer - so if (like me) you have been using Tortoise for years and don't have svn.exe - just re-run the Tortoise installer selecting the option.
Fixed - many thanks