Very sorry to hear of your loss, please accept my condolences
Legally there is nothing to stop you from holding a funeral in January.
The main issue to resolve is where to keep the body until then. Does the undertaker have space and if so are they willing to do so.
Also to be born in mind, especially following the past 18 months, is covid19.
Today new isolation rules were announced for some South African countries for fear of yet another new type of covid19.
Also the worrying rise in Europe and the fact that the UK despite playing down figures there is still a worrying number in the UK, more than 47,000 new cases in last 24 hours.
There is always the risk that restrictions could be reimposed at very short notice if things get out of hand in th UK as there are in a number if other areas, and during last lockdown etc numbers were limited to very few for funerals.
Just something to bear in mind.