mines a 58 plate and hasn’t been serviced by a main dealer. always goes to a specialist. as long as they use genuine parts it doesnt matter if it is serviced by a main dealer or not. as for modifying your car its a risk you have to take. some dealers will honor warranty claims others wont. but in 22,000 miles it hasn’t put one foot wrong. as was only standard for around 3,000 miles.