Problem with a mixer shower taps

Hi, I have a mixer shower taps made by Sirrus and they are fully thermostatic. It has been working fine for the last 3 years, that is until yesterday, the hot water has ceased running thought it and now I only have a cold water flow thought the taps. Does this sound like a very expensive plumbing job or would it be cheaper to replace the taps, or is it something very simple like a washer need replacing? I still have hot water in my kitchen and the bathroom sinks so it's not a hot water problem. If I remember they don't come very cheap this type of taps. I live in the London area and plumber's are like rocking horse sh*t at the moment.
Thanks in advance....Jayne
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Does the head feel loose when you turn it ? Can you open the tap fully and pull / push the head gear up and down ?
It could be washer has fallen off the end of the plunger and is stuck in the hole the water should come out of. It could also be that the whole plunger has fallen out of the end of the thread in the tap lifter.
Remove the tap head and undo the lifter gear from the body of the tap and you'll find out what happened inside. Remember to isolate the hot water system from any heating appliances before turning it off and draining it down to work on the tap.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sorry Jayne, forgot to add the link in my reply: :-))
http://www.diynot.com/pages/pl/pl025.php
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.