Crypto asset airdrop

HI, According to CRYPTO21250 - Cryptoassets for individuals: Income Tax: airdrops https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto21250 Do I have to pay income tax if I get airdropped tokens only because of holding a different token? Do I have to pay income tax if I get airdropped tokens because I have been told if I lock up a specific token for a period of time than I will have get x amount of new tokens? If I get airdropped tokens what is subject to income tax and I only know the USD value of it how do I specify the exchange rate to GBP. Let's say that a new token is generated and airdropped on the same day at 11:35 without any known price value and than the token is available to trade on exchanges from 12:00 with the starting price of $0.1 and than the price fluctuates between $0.10 and $1 on that day. What price do I have to use to calculate the GBP value for the income tax? Thanks.

Hi,
You can see guidance regarding Income Tax and Capital Gains Tax here:
Cryptoassets 
Under the terms of Self Assessment, we do not provide an official exchange rate and the onus is on the individual to use a just and reasonable exchange rate for each acquisition and disposal. For your convenience, there are exchange rates here:
Exchange rates from HMRC in CSV and XML format
and for older rates here:
Foreign exchange rates and spot rates: 1 January 1989 to 31 March 2009
You are free to use any of the supplied rates or one of your own choosing.
Thank you.