Hello welcome to the site.
I have reviewed the contract and point you to the following clauses:
7.3 We are not responsible for delays outside our control. If our supply of a product is delayed by an event outside our control then we will contact you as soon as possible to let you know and we will take steps to minimise the effect of the delay. Provided we do this we will not be liable for delays caused by the event, but if there is a risk of substantial delay you may contact us to end the contract and receive a refund for any product you have paid for but not received
It has been 6 months, so that is a substantial delay
8.2 Ending the contract because of something we have done or are going to do. If you are ending a contract for a reason set out at (a) to (e) below the contract will end immediately and we will refund you in full for any products which have not been provided and you may also be entitled to compensation
(c) there is a risk that supply of the product may be significantly delayed because of events outside our control;
(e) you have a legal right to end the contract because of something we have done wrong.
They are in breach of 8.2 c and e. So to address your question then yes you do have legal ground to request a refund as per the contract.
I hope this helps, and would be grateful for a positive rating, thank you. John