You should have been given a 'written statement of employment particulars' (which, although not a contract, per se, includes many contractual rights) on the day that you started work:
https://www.gov.uk/employment-contracts-and-conditions/written-statement-of-employment-particulars
It would seem reasonable that, if an employee was to mislay such a statement, the employer should then provide a further (unamended) copy of it.
Information about how changes to your contract of employment should be made can be found here:
https://www.gov.uk/your-employment-contract-how-it-can-be-changed
Acas provides a free helpline service for enquiries about employment law. Several AB members have stated that, although it can take a while to get through, it's well worth the wait. Call 0300 123 1100 between 0800 and 1800, Monday to Friday (although I'm guessing that the line probably won't be staffed tomorrow, as it's a bank holiday). Under Ofcom rules, calls to 0300 numbers must be charged at the same rate as those to 01 and 02 numbers, from both landlines and mobiles. So, if you've got spare 'included minutes' in a call package, the call will then be free.