I thought i had it with an IF formula, but i completely read the email wrong.

First/Second time buyers:
- On the first £250,000 of the value of the property 0%
- Balance above £250,000 up to £350,000 5.5%
- Balance over £350,000 3.5%

Third time (or over) buyers:
- Value of the property up to £200,000 0%

- Value of property between £200,000 and £350,000 2.0%
on the first £250,000 and 5.5% on anything exceeding £250,000

- Value of property exceeding £350,000 3.0%
on the first £350,000 and 3.5% on anything exceeding £350,000