Try downloading it from:
ftp://client.coh.com/EU/MAC_CoH_Installer_EU.dmg
That seemed to work fine for me.
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Thank you! That seems to do the trick. 
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I may be being thick here as I'm not really a Mac person, but I do have a nice new macbook and sat in a bar with free wifi tried downloading the mac client.
The US client downloaded 1st time - no problems... but I haven't tried that as my 14-day temp US account died about a year ago (I downloaded the US client by mistake).
I've tried to download the EU client 6 times - it fails each and every time.
The last time I kept the 'Downloads' window in focus, and clearly saw that the client download went fine until it was (apparently) 100% complete and then threw an error ('The operation couldn't be completed (SafariErrorDomain error 2))
Anyone know if I have a 'known' error or am I blatantly doing something wrong?
Many thanks in advance.
By my mohawk shall ye know me!
my toons
Funny: Ee-Ai-Ee-Ai-Oh! #3662 * The foul-mouthed Handyman! #1076 * City of Norms #132944
Serious: To Save A Single World (#83744) * Marketing Opportunity (#83747)