if a question is asking me what procedures i should preform at the year end to confirm the value of purchases included in the income statement am i right in thinking they are refering to inventory?
No, the question should mean what it says: it is referring purchases. Income statement amounts need to be audited too. So, substantive tests would involve inspecting invoices to make sure they related to purchases (and not, for example, non-current assets) that purchase tax had been removed and that cut-off was correct.