Standardised outcome measures will be collected at baseline, intervention and follow up phases. Participants will also be asked to collect daily idiosyncratic measures in between the intervention phases. Participants will be randomly allocated to differing lengths of baseline to the time of the intervention with 4 potential arms (7 days, 10 days 14 days or 17 days). This will be done using a simple spreadsheet by a Research Assistant at CADAT. The baseline discussion around the memory of vomiting, imagery re-scripting and treatment planning will consist of 1-1.5 hour sessions. Time intensive treatment will consist of two sessions over 2 days (4 hours each). Three additional follow up sessions will be administered, 2 within 1 week of the intensive days and a third 1 week after the second follow up session. The same standardised outcome measures will be collected at 3, 6 and 12 months by phone or post.