Well after tracking down another retailler who 'alleged' to have stock I ordered the part, this time from B&H in the states. This will be the first time I've ordered from the states [as far as I can recall] so I'm eager to see how this shapes up.
I have had confirmation that this has shipped now and will be coming to be for $65 which equates to around £33 and I potentially need to add VAT [@ 17.5%] to this figure so the final could be £39. Expensive for the adaptor but I'm just relieved I will be able to use the MT 24-EX again and get the best out of the 180mm Macro.
Hopefully I have the adaptor for this weekend, should allow me to get out and about taking some shots. I have thus far been under-whelmed by my efforts with the lense but thats mainly down to lighting and local conditions. We'll see what the future brings.