The first question that should be asked is, is this an "official" noise abatement procedure. If its not in the AIP then it would appear that either it isn't, or the aerodrome have failed to notify it. Are Aerodrome Standards at the CAA aware of it?
For self protection the FOB should state that turns after take off shall not be commenced below 500 ft and with no more than 15 degrees of bank. Where a noise abatement procedure requires a turn below 500 ft, then further minima should be specified, to include Speed, an absolute minimum height and possibly configuration.
At a Midlands airfield the procedure calls for a 30 degree turn immediately after take off. The FOB should establish where Take-off ends i.e. not below screen height, ideally not before the end of TORA and not below a safe climb speed! If all these items are covered its about as safe as it can be.