Cold calling UK offices from US

I'm a junior with a couple of back office internships and slightly low GPA at an emphatically non-target school. I will be traveling to Europe towards the very end of the summer to take a somewhat relevant class at a well known school.

I'm also in the process of lining up something in town that isn't IBD but is pretty strong and has helped kids place into baking in the past. However, I was thinking about trying to find something in IBD somewhere in the UK prior to the class as I only speak English fluently... obviously London but also open to anywhere.

I've looked around on M&I for general cold calling strategies and found some useful info from an admittedly half-assed search on this site, but I wasn't able to find anything in-depth relating to this topic specifically.

I was wondering if there is anything I should keep in mind or expect when calling. Time of day preferences, disparity in customs, etc. Also, in light of my unimpressive credentials, would a firm across the pond take a chance on an American kid who ostensibly does not ball hard? Or should I expect a "Piss off, wanker," and an abrupt hangup?

Any input is appreciated.