As far as I'm aware, Scotcall is a trading name of Shieldaig Enterprises Ltd. The Companies House website is closed at the moment, but you could look when they are open to see if they are a subsidiary of any other company.
You could for a fee get details of their directors and see if any match, and the BCW Group plc accounts should give a list of their subsidiaries, if any.
Does Companies House hold records for partnerships and trading names?
Many plc's make up the name of a firm to put onto letterheads in order to intimidate debtors. Don't always assume that threatening letters come from established firms.
Buchanan Clark & Wells are debt collectors working in Solihull and Glasgow. A posting here on 29-05-2004 details some experiences of dealing with them.
Scotcall Debt Collecting Services have a website at scotcall.com. I didn't get past the flash animations, but I suspect there isn't much on the site.
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