Has anybody actually located Spancilhill yet?

If not, it's on the R352 road about 4 miles NE of Ennis (mostly east).
The name is a misnomer for Cnoc Fhuarcoill, "Hill of the Cold Wood", as the F was aspirated and omitted in local speech to create another name, Cnoc Urchaill, "Spancil Hill". The Irish word "urchall", or "urchomhal", means a spancel: fetter or shackle for the fore or hind legs of an animal. (Source: A History of Clare by Sean Spellissy, Gill and Macmilla, 2003.)

Kieran Sheedy, author of "The Horse in Clare" [sounds like a fascinating book!] (2001) writes that King James I granted a patent in 1621 to allow a guy called Valentine Blake "to hold a fair and collect tolls". The fairs, then mainly for pigs, cattle and sheep, were held on 1 Jan, 3 May, 20 Aug and 3 December. A separate horse fair a held on 24 June. (same source as above).