Car done 100,000 exactly, so a Spring clean of the engine might be in order
I don't want to go down the Terra Clean route, also when I last had an MOT
they said the hydrocarbons were high.
Have a look on youtube first, lot's of videos on there showing the differences of product strength/effectiveness. See if you think it's worth it.
BG44k is quite good but you'd probably want to do it several times, these things aren't a one shot thing unfortunately.