The figures quoted are just that "Guidelines" and simply provides an indication as to what an injury is worth.
No two claims are ever the same and the overall value will depend on the severity of the injury, the personal circumstances of the individual concerned and other relevant facts.
There are also upper as well as lower limits not to mention the inbetween limits which is why the independent medical report is so important as it will give a long term prognosis which is by and large how a case is valued.
If you feel that your solicitor has undervalued your claim, you are entitled to change firms, but I would suggest that you speak to them first and express your concerns, and remember your solicitor cannot accept a claim on your behalf without first consulting with you and providing appropriate advice.