Speeding up to let others past

[Quhet]

Because my girlfriend is currently in North Yorkshire and I live in the Midlands, I've been doing a fair bit of driving lately to see her.

More often than not, I use cruise control and set it to a sat-nav indicated 75mph. I try as hard as possible to maintain consistent speed by generally being aware of my surroundings and I resent (rightly or wrongly ) having to increase or decrease my speed. On a couple of occasions knobheads have come haring up behind me whilst I'm overtaking and become annoyed that I'm not seemingly doing more to get the overtaking done with and pull in to let them past. Obviously going quicker than those I'm overtaking, I can't pull in but similarly I could accelerate and go a bit quicker.

I wouldn't pull out to overtake if it wasn't safe and if I felt that I'd be holding someone up but if I'm say doing 5mph faster than a line of cars in the middle lane, it could take me a couple of minutes to finish overtaking by which time there may be a line of white S-Line Audi Tdi's behind me frustrated that they're not going 90+.

Am I being unreasonable?

[Quhet]

I guess it's give and take.
I've got no problem with people going quickly on the motorway, but people don't have a right to flout the limit and go much quicker than everyone else, bullying people who are slower than them out of the way.

[Quhet]

Interesting points all, thanks for your input.

To make it clear, I'm not just bimbling along in the outside lane at 70 and not moving in. Only a couple of cases where I've been mid overtake and a car has come steaming up behind me desperate to get past.
I blame those knobbers who speed up as soon as they see you pulling to overtake....

At 75mph, I'm normally the one in the inside lane that everyone is flying past