You have been with your husband for 15 years but married for 6 years and have no children together. How long had your husband owned the flat before you moved in? How long were you living in the flat before you married? How long were you living in the flat after you married?
Did you contribute towards the mortgage or pay your husband rent, whilst living in the flat? Did you contribute towards bills whilst living there? If so, can you prove it? Eg. Bank statements. If you financially contributed whilst living in the flat, it's possible you may be awarded some of the £200K but certainly not half and being awarded anything at all isn't guaranteed.
The savings your husband has is a martial asset, and in theory you might be awarded half. The fact you don't have savings isn't your husband's fault. By admission you admit you earn a decent salary and have chosen to spend rather than save.
However, if your husband is older than you, and closer to retirement, his earning potential will be significantly reduced. You are younger, have working years ahead of you and earn a decent salary, so your needed may be deemed lower.
Your are on the mortgage for your current home as it's jointly owned with your husband. You are liable for half the mortgage, and if your husband stopped paying his half, the full amount! Of course, you will have to pay your half of the mortgage and any rent you are now occuring. Assuming you did receive £475K for the property, it's only made £10K since it was purchased. You would receive half of the £10K. The property market at the moment is dreadful, nothing much is selling, unless it's priced to sell.
You need proper legal advice. You will be asked the questions by your solicitor, as I have asked. So make sure you take any evidence of money you contributed whilst living in the flat. My honest opinion is, you will need to lower your expectations considerably.