I see that you live in the UK and hence I would ignore suggestions by plastic surgeons in the US who feel that 400cc is a good size implant for you. Looking at your photos, you do seem to have reasonable amount of your own breast tissue and I do feel that 400cc might be too big for you. Ladies in Europe usually do not opt to go as big as ladies in the US! You need to be examined in person to determine what would suit you best. When choosing an implant, the surgeon is guided by what the patient desires. It is then essential for the surgeon to examine you, take some measurements and recommend what would suit your body. You breast base diameter determines what size implant you can have and how big you can go, and yet look natural. Although, various morphing softwares can help give you an idea of what your augmented breasts might look like, it is important for you to try sizers in garments to help you get a 'real' 3D feel and also give you an idea as to what it would feel like to carry that extra weight. The Biodynamic breast analysis system is an excellent method of helping patients choose their implants. Whilst it is nice to have larger boobs, it is equally important for them to look as natural as possible. As a general rule, the larger the implant, the harder it is to hide them. One should also take in to account the weight of the implants. The larger the implants, the heavier they will be and this can have adverse effects on your breast envelope. The breast can end up being droopy with a stretched skin envelope in future if the implants are heavy. This may necessitate reducing the volume of the implant and doing a breast uplift procedure in future. For optimal outcome, please consult a fully qualified plastic surgeon, who has specialist qualification in plastic surgery 'FRCS Plast' after having being trained adequately in the field of plastic surgery, is registered on the 'Specialist register for Plastic surgery' with the General Medical Council and has been considered competent enough to be a member of the 'BAPRAS' (British Association of Plastic Reconstructive and Aesthetic Surgeons) and 'BAAPS' (British Association of Aesthetic Plastic Surgeons) at the least.