What a great forum, I was pleased to see this old thread is still going, I am about to buy a 151EN (and a argon/CO2 mix big tank and regs etc) from machine mart and after doing the welding I need to do on the truck I will have a proper good read thought all this and doubtless have some questions, great pics as well
You can get conversion kits for under thirty quid then you just need to add a euro torch of your choice.
Weldequip do all the bit's but I can't see them on his website so here's the first one a google search brought up: https://www.welduk.com/product/mig-gun-euro-torch-conversion-kit
If you need to buy a new gun and a gas solenoid I expect to need to pay around £80. It's something I've thought of doing, but hesitant about spending that much on a modest machine, which works as it is.