Hello Graeme
Based upon your description of the model and equipment I would snatch the chaps arm off and run away with the model before he comes to his senses.
Paul
I will add the caveat that I haven't seen the boat or equipment and that I am not an expert on steam, my opinion about value is based purely on what I perceive as the resale value of the items. I would strongly advise that you contact a local steam model engineer for a more accurate appraisal.