ACR X ON OCEANIC RTE HAD ALT CHANGE TO AVOID CONFLICT LTSS.

Narrative

ACR X DEPARTED PARIS ORLY TO PHL FIELD NAT J WHICH BEGAN AT 4808N; THE TRANSITION TO THE NAT SYS WAS FROM FRENCH AIRSPACE UNDER BREST CTL. CLRNC FROM SHANWICK OCEANIC WAS OBTAINED APPROX 45 MINS PRIOR TO TRACK ENTRY. AT THAT TIME OUR CRUISE ALT WAS FL350 AND THE REQUEST WAS FOR TRACK J FL350 MACH .80. THE CLRNC WAS RECEIVED; READ BACK; AND ACKNOWLEDGED. OUR CHANGEOVER TO SHANWICK BY BREST WAS VERY CASUAL AND WE REQUESTED A CHANGEOVER ABOUT 25 MI FROM 4808N. AT 4808N WE MADE OUR FIRST POS RPT. APPROX 12 MINS LATER WE RECEIVED AND ANSWERED A SHANWICK SELCAL. SHANWICK GAVE US AN IMMEDIATE DSCNT TO FL330. AFTER THE DSCNT WE REQUESTED THE REASON. 10 MINS LATER THE REPLY WAS THAT BECAUSE OF VARIOUS OTHER ACFT REESTIMATING THERE WAS NOT SUFFICIENT LONGITUDINAL SEPARATION ON THE TRACK. 2 HRS LATER AT 30 DEGS W WE REQUESTED AND RECEIVED CLRNC BACK TO FL350. 1) I FEEL THERE SHOULD BE MORE COORD BTWN BREST AND SHANWICK IN THIS AREA. AT TIMES WE ARE CHANGED TO SHANWICK WITHOUT BEING GIVEN A FREQ. 2) THERE IS GREAT EMPHASIS PLACED ON TRACK CHANGES; IE; IF GIVEN A TRACK OTHER THAN THE ONE REQUESTED ALL COORDINATES OF THE NEW TRACK MUST BE READ BACK TO CLRNC. WHEN RECEIVING THE FILED TRACK THIS IS NOT REQUIRED. I BELIEVE JUST AS MUCH EMPHASIS SHOULD BE PLACED ON NEW ALTS; IE; 'FL330 NOT AVAILABLE; YOU ARE CLRED FL310.' NORMALLY NO EMPHASIS AT ALL IS PLACED ON AN ALT CHANGE UNLESS IT IS HIGHER AND THE QUESTION BECOMES; CAN YOU MAINTAIN THE HIGHER ALT?