A service might be a good place to start.

Blue smoke and the mileage you've done may suggest that the valve stem oil seals are past their best, they can be replaced fairly cheaply if the car is worth saving.

First job then is a service - a proper one.

Sump plug out, oil filter off, drain oil completely. New (high quality !) oil filter, new sump plug crimp washer when the plug goes back in, The correct grade of oil. New (good quality) spark plugs. New (high quality) air filter.

Do you REALLY know how to do your own vehicle maintenance, or not ? Remember, if the answer is 'I'm not sure', then the answer is probably 'No'. In which case those jobs would need to be done by a garage. Which will probably charge you anything up to £250 for that work. If you're lucky, you might know someone who is actually competent in home maintenance, who might do it for you for beer money. (though remember that a person good at maintenance isn't working under the bonnet every weekend).

Can't afford to keep a car well-maintained ? I got news for you. Lack of maintenance is more expensive then proper maintenance.