Visa extension done in time, overstay if rejected

[nedders]

Hi

1) If I apply for a visa extension to a standard tourist visa and pay the fee (approx. £1000) prior to expire.

If it is rejected, as long as I leave immediately or prior to their decision, will I still be classed as an overstayer? (As the application would have been made prior to the expiry date)

2) ps. Might need another post for this but if one enters the UK for tourism and is granted 6 moths, is one able to switch / extend for a private medical treatment?

[secret.simon]

What are the grounds for extending a visit visa? They are quite rare.

[nedders]

I came to UK for tourism.

Unfortunately 1 month in I was in hospital.

As a result I wanted to do a private medical treatment, but it would overrun my stay