Andrea,
The first suggestion I have is to read through this site.
http://www.romantasy.com/[...]er.html
Romantasy is one of the finest corset makers today. They are very TG friendly and supportive.
ROMANTASY is happy to welcome inquiries and orders from any transgendered MTF corset enthusiast be they crossdresser or transwoman, who has a serious interest in learning about and creating a more authentic female silhouette through quality custom corsetry. (In addition, ROMANTASY now welcomes the transman They are, however, in the US.
This link is to the Men/Transgendered Male section. It will teach you a lot about how to make sure your choices are the correct ones and that the company doing your corset is competent to do one for a TG male body. Reading the rest of the site is enlightening toward being sure that they are good corset makers overall. It will also teach you to care for a moderately expensive investment and about the ancillary equipment like a lacing pole or device, what to wear and not wear under a corset. You may find that you actually want two corsets, and undercorset and and overcorset. A good first choice is an underbust corset. For the very serious lacer there is tight lacing and actually reshaping your rib cage into a more feminine shape, raising your natural waistline. This requires great dedication.
You will by now have realized that I'm not suggesting an off the rack corset. One that will fit well, be comfy and do the job you want is best made to your body measurements.
http://www.romantasy.com/[...]g.shtml Good corsets are best made when the corset maker measures you. Be sure to bring a half-slip....a gaff if indicated by your personal responses. You will be expected to behave like a lady or at least look like you are. If you want an overbust corset you will need to bring your forms and attach them or bring a bra. Some makers will go on your measurements but you bear responsibility for those. Romantasy asks for body photographs so they can create just the right corset. They will also send you a mock-up made of inexpensive material for sizing before doing the actual corset. You try it on, and let them know if there are any issues with the fit. Do NOT try to take your own measurements, they change when you move to take them. Heisenberg's Uncertainty Principle applies when measuring yourself for clothing. If your corset maker is not asking for all these measurements and information, you might want to ask yourself why. Remember that your corset will only work properly in a certain range of waist sizes. If you lose or gain too much weight you will need another one made. Reduction beyond 3-4" will take time and dedication by you.
Expect an in-person consultation fee. For this you will receive a number of valuable services. These include correct fitting, viewing/touching actual examples and fabrics, and good advice on your choices to meet your needs. Consider it part of the cost of a good corset. If you buy two or more, you only pay it once. Over time, however, your measurements may change and your old corset will stretch so don't be fooled. In fact you must carefully stretch it gradually after you receive it. If you don't, it may tear the fabric. More expensive fabrics can add a great deal to the garment's cost. You must give it proper care for each wearing.
Seems like a lot of bother, doesn't it? You asked for a decent corset. Expect to wait at LEAST a month for your corset. Don't be surprised if it is longer, particularly going up to summertime, like now. Proms and weddings put a demand on the makers.
Here are some googled sites for you to check out. in the UK. I cannot recommend any, myself. Hopefully some of the other girls will know of good ones in your locale.
http://www.google.com/sea[...]=images 
