If I buy a bike on my credit card and then transfer the cost to a 0% card can you transfer only that amount rather than my usually monthly outgoings or is it like a new current account where one closes and another opens?

They both stay open and you transfer whatever amount you want.

Awesome…point me to a bike shop

Or get a card that’s set at 0% that you can buy the Bike on. Saves swopping over.

http://www.moneysavingexpert.com/credit-cards/best-0-credit-cards

Note that some smaller bike brands – Cotic etc – do 0% credit if you buy direct. eg http://www.cotic.co.uk/finance/

If you transfer the balance then you will incur the transfer fee. Check what that is as it maybe better to open a new card with 0% on purchases as said above.

Check what that is as it maybe better to open a new card with 0% on purchases as said above.

Yep 1.5% for 24 months seems usual but like you say can be avoided.