The amount you receive for an ankle injury can vary depending on how severe the accident is. If there will be permanent symptoms, the payout is likely to be higher too. Here's a breakdown taken from the 17th edition of the Judicial College Guidelines, which gives you an idea of potential awards:
Very Severe £61,090 to £85,070
Severe £38,210 to £61,090
Moderate £16,770 to £32,450
Modest Injuries Up to £16,770