Passport returned becoz of Wrong Application Fee - URGENT

Hi,

I had applied for Tier-2 Visa extension, and as per the UKBA home site application fee is 350 pounds. But Today I got my passport returned saying "although payment has been done, it is not correct amount and will be returned shortly. You must pay the full amount when making your fresh applicaiton to the adress given on the app form....."
Now I have a valid CoS but VISA has expired.

2 questions.

1. Can I return back to home country as i have my passport now, will there be any issue during the immigration check as my visa is expired. If yes, what all documents I need to carry to suffice.

2. Can I re-apply with the correct amount for extension again. What is the correct application fee for extension, the letter doesnt say anything about the correct fee to be paid.

Any suggestions please.. I have take action today itself

the "correct fee" is stated on the application form itself, where you fill out card details.Question A1.

If you leave UK, then your employer will need to issue you RESTRICTED COS. This is harder to get as compared to un-restricted COS.

i think you can submit new app while remaining inside UK, as long as its not been more than 28 days since your visa expired.

If refused again, you will not get the right to appeal.

Also, if more than 28 days have elapsed and your second application is also refused, then 1 year automatic ban could be applied

http://www.ukba.homeoffice.gov.uk/aboutus/fees/

2. Depending on your luck, if immig officer notice that you have over stayed, then (s)he will stamp your passport

I had mentioned exactly the same amount as specified in the UKBA website.. Weird...

Anyways I have decided to travel back immediately... Will the acknowledgement from UKBA on application submission and also return letter will suffice to clear the immigration checks or should I carry any more documents from my Company's Management ??
I want to avoid hassles during immigration.. Please help... Thanks