you are right " everyone else has one" is a rubbish reason for spending 7K.
you need to do a proper analysis of this situation. Answering these questions should help you
You currently heat your rads using an oil boiler. Does this boiler need to be replaced ? Are you happy with this solution. if not, what are you not happy with ? If it is the oil bill, then you can take steps to address this - is your house well insulated ? can you make your system more efficient by having a powerflush ? replacing rads ? etc.
If you need to replace the oil boiler, then you have a choice of a new oil boiler or a stove. What are the pros and cons of both systems and what do you want of your heating system.
If you want to be able to control the heating via a timer and have it come on before you get up in the morning or come home from work, are you happy to lose this by having a stove heat the rads ?
What is the fuel cost saving of the stove vs oil ? you need to find an answer to this, from someone with a similar sized system.
If this is supposed to be about saving money and you are replacing a good oil boiler, you can do a lot of save oil without replacing the whole system and if you need to replace the system, take a long hard look at what you want before you decide.