The link between exercise and mental health is well known. Many people find the motivation to exercise  hard, or need expert guidance on exercising safely when experiencing an eating disorder. A personal trainer through a local gym or someone who comes to your home is a good way of getting motivated. However it can be expensive wit most trainers who are experienced charging £50+ per session. Some guidance if personal training is something that appeals to you. Never choose someone who has stuck a leaflet through your door, advertises in yellow pages or has a big advert somewhere unless you have checked out their qualifications are genuine, they have insurance and they should be Enhanced CRB cleared. They should ideally work with the public in some way other than just one to one, in homes, ie in a school, a gym, etc so you know they are legitimate. Never hand over  money for more than one session at a time and don’t ever feel pressured to buy block sessions until you know for sure say after 6 months that you are enjoying the sessions.  The trainer should push you a bit but never excessively so you injure yourself.  

There are a few good registers to look at to find a good trainer.  The Register of Exercise Professionals is one