After allowing for claimable expenses I have a Capital Gain

1. There are two things you should be considering here. The first and best thing would be if you could put half of the assets you are selling into your wife's name, as she also has a 750,000 exemption for retirement relief and you could use this to remove any CGT tax altogether. For example if you put approximately a third of the value of the assets in her name so that she received a third of the sale price, then no tax would be payable as transfers between husband and wife are CGT free and she would be able to use her allowance.
2. The second thing is Marginal Relief. This essentially states that where the money received for the sale of qualifying assets is above the 750,000 threshhold, then tax will be reduced to half of the excess over 750,000. That means that the maximum payable would be 127,500. However, as your tax payable is only 62,500 this is not of assistance.
3. I would recommend that you get some tax advice and a little help to set up the situation for the maximum tax relief.