Thanks Jason,
It is just metric I'm after, I have noticed they cost almost 50% more than an imperial set of similar sizes – although only ArcEuro seems to sell them as a (budget) set.
I've been on Steelmans website this morning, and after going around and around the net I landed on Rotagrip at around £30 a broach delivered (I'll take some of their metric 123 blocks too since they're so well priced) although their ebay customer service did tell me that they are out of stock and do not know how long resupply will take, so I suspect purchasing on their website will yield a similar result.
I need to key a 10mm hole with a 4mm key, and I'm not sure if this is even possible – Arc's set only goes down to a 12mm bush and it looks like that could be the limit without getting creative. – I will have to double check that size tonight.
Edited By Russ B on 25/03/2014 15:32:29