The amount of grant you get is decided on an individual basis. You will receive the difference between the total cost of the adaptations the grant covers, and the contribution (if anything) that you will be making.
The maximum grant is £30,000. Some large ground floor bathrooms and bedrooms extensions do cost more; the council has the discretion to pay in excess of £30,000. Each case is assessed on its own merit and where there are genuine issues of hardship or inability to fund these works an additional sum may be agreed.