Upvote:4
According to gov.uk, you need to show the following for a Standard Visitor Visa:
youβll leave the UK at the end of your visit
youβre able to support yourself and any dependents for the duration of your trip
youβre able to pay for your return or onward journey and any other costs relating to your visit
you have proof of any business or other activities you want to do in the UK, as allowed by the Visitor Rules
For 1, I would suggest documents detailing job offers (if outside the UK) and a letter from your parents saying you have been living there and will return (if this is the case). The letter from your Grandfather along with his bank statements should tick 2 and 3 (read this document Section 4 about sending too many documents). For 4, you are required (here) to have a letter (I would definitely recommend hard-copy) from the GMC that you are entered for the exam. As regards whether you will be approved, as a well-qualified doctor with family in the UK I see no reason why not. But the only way to find out is to apply.