Hi. I'm not an OVH staff member, so these are not official answers, but it may anyway help you.
OVH web hosting is not assisted or managed, so they will not help you on installing software or anything else, unless it's something related to the usage of the OVH manager and/or other tools provided with the service.
OVH shared hosting servers are located in their datacenters. Most of them are in France(RBX,SBG,GRA), and some are in Canada(BHS). I see no option to select datacenter, so not sure which will a new hosting plan end up in. Also, OVH offers cache points of presence, which will accelerate the content delivery for static contents(images, scripts, css, etc). That is explained here:
http://www.ovh.co.uk/web-hosting/geocache.xml
The ping time may vary by country & ISP. Here is a page where you can test the speed to different OVH datacenters:
http://proof.ovh.net/. Also, you can ping directly to any of the hosts listed in that page.