3. Proof of financial support
* evidence that you can support yourself and accompanying family members while you study in Canada. Such evidence may include:
o proof of a Canadian bank account in your name if money has been transferred to Canada;
o your bank statements for the past four months;
o a bank draft in convertible currency;
o proof of payment of tuition and residence fees;
o for those with a scholarship or those with a Canadian funded educational program: proof of funding paid from within Canada.
* if foreign exchange control measures exist in your country, you must provide proof that you will be permitted by the exchange control authorities of your country to export funds for all of your expenses.
It doesn't say anything about your uncle co-signing for you being acceptable but maybe it is. You might want to discuss this with the embassy in the UK before you apply.