I got taught Coldfusion at Uni and so far on the job hunt its seems PHP is the language to go for. I got told by one potential employer that only a very small percentage of people use coldfusion .....

Im switching to PHP, im no expert but from what ive seen Coldfusion doesnt seem to have the biggest market ! There hosting can be a little more money as well ...

It's unique to your area. Go to job sites like Monster.com or careerbuilder.com. Search different web development languages. Does coldfusion list 100 jobs? Does php? What about .net? If you are strictly learning a language for financial gain or employment security, this is what you should look into.
Getting paid is not about knowing one thing. It's about combining a potent and popular combination of skill sets and knowing how to do them extraordinarily well. When you see the search results for the jobs listed above, what other required skills are listed? For php, you'll probably see Apache and MySQL. For .net, you might see asp, vb, and/or C# plus the visual studio and sql server. The ultimate "GET PAID" stack is probably Oracle and Java. You know Oracle and Java and you are a made man! Whatever you do, stick with it and become an expert. You will not get rich by knowing how to output "Hello World" in 15 different languages. You will not get paid by knowing how to do a select statement in 18 different databases. You will get a great paying job for knowing the granular details of one specific skill set combination that is currently in demand.

IMHO, ColdFusion is very viable. Especially the newer releases, 8 and now 9. CF8 added tons of AJAX functionality, and 9 takes it to the next level. CF is definitely a Rapid Application Development language that allows you to build data driven sites and applications quickly and easily. Thanks for the question.