Does a voluntary termination of a conditional sale legally have to be in writing .

[Guest]

Hi I used my right voluntary terminate a conditional sale on a vehicle,but after doing so,I wished to change my mind and I asked if I could set up payment plan instead, they flatly refused, well because of the covid-19 outbreak,they were supposed to collect the vehicle on the vehicle on March 14th.but they sent me an email saying they could not collect the vehicle at this time,and could I please keep the vehicle taxed,mot'd and insured,the mot had run out in February, I had to change the insurance to my wife's car,I am disabled so have cancelled the tax as I have also put this on my wife's car,they want me to keep the vehicle until the outbreak of covid-19 is over,which could be months,they could charge me for the vehicle as it would have been sitting without being used for over 6 months,so I have decided to charge the finance company storage charges at £10 a day,can I legally do this as it is not my fault they couldn't collect the vehicle, I know it's not their fault either,but I did offer to make half the payment a month, and they refused,also will the vehicle still show on the hpi register as being on finance. Many thanks. Darren