Does anyone know any good, inexpensive presentation training courses/events (ideally below £100... I cannot get approval for any that cost much more than this without drawing unwanted attention to my 'inadequacy' in this area).

You are unlikely to find much for this price but if you are in Manchester you could try the Pace network or look for something similar in your area. We cover training in this area but it is normally arranged for groups rather than individuals. However, if you are in the right area we may be able to help you. Call me on 01625 438888. Regards, Sylvia