Here are a few special events/call-signs I know about for today…
2MT – 3.663 MHz – 0900 to 1600 UTC (Chelmsford ARC)
GB4LZP, GB0WHR, GB2COB – Meirion ARS from Welsh Highland Heritage Railway
Porthmadog & District ARS operating from Marconi site at Nebo Anglesey
Telford ARS operating from Marconi site at Tywyn
GB0MBS – 1700 UTC Friday 29th to 2259 UTC Saturday 30th
Many UK call-signs have the special “R” in their call-signs as well so be sure to catch one or two if you can!