I have been paining over this for ages but after finally trawling the web I finally found a post which was soooo simple but very effective in clearing the consumed memory. Link to post

What I did do was take it a stage further by building it into my Application.cfc so upon each request I would check for free memory and run the garbage collection accordingly if required.

In the OnRequestStart section I added the following code (Remove the CFFILE part as that's only there so I can see when ColdFusion does clear the garbage - Plus you can alter the free memory limit depending on your personal tastes):-

    <cffunction name="onRequestStart" access="remote">
    <cfargument name="targetPage" type="String" required=true/>
        <cftry>
            <cflock name="checkMemory" type="exclusive" timeout="1" throwontimeout="yes">
                <cfset runtime = CreateObject("java","java.lang.Runtime").getRuntime()>
                <cfset freeMemory = runtime.freeMemory() / 1024 / 1024>
                <cfif freeMemory lt 100>
                    <cfset objSystem = CreateObject( "java", "java.lang.System" )>
                    <cfset objSystem.gc()>
                    <cffile action="write" output="Garbage collected at #now()#" file="c:\garbage_collection.htm">
                </cfif>
            </cflock>
            <cfcatch type="any">
                <cffile action="write" output="Garbage collection failed at #now()#" file="c:\garbage_collection_failed.htm">
            </cfcatch>
        </cftry>

      ... YOUR CODE GOES HERE ...
 
        <cfreturn true>
    </cffunction>

Now, I haven't yet evaluated any performance penalties on a live server but I'm prepared for a small hit if it stops the server running out of memory then I'm happy.