We arrived in London after a 14 hour flight from Kuala Lumpur. I think that is long enough for a single journey, and I am glad we planned a break in KL. The 24 hour direct flight from Australia to London must be hell.
After a bit of time with the hire car company, as they were charging us exorbitant extra costs on our hire car, even though it was all pre paid, we jumped into the car and started the drive to Brighton. We hired a little VW, and it had no problems doing 80 MPH on the motorways down from Stanstead airport. Problem was that everybody else was doing about 100 MPH (about 160 KM/H). We were even being passed by transit vans.
Arrived in Brighton at about 6pm and found car parking a bit of a problem. The cheapest parking place was about $30.00 per day. After parking the car all we could do is sleep. It was a big decision to sleep however because it was only 7.30pm and the Brighton festival is on until tomorrow night so people everywhere ready to go out and hit the town. There was people everywhere and still very light but we made the decision that sleep was very important by then as it was about 1am KL time and we had been up since 6.30am.

You have found one of the major problems with visiting Brighton, its car parks are very expensive. It once cost me £15 for 2 hours. This is a council policy to reduce car traffic. There are much cheaper park and ride facilities just a little way outside of the centre, so if your not staying overnight then i would go for that option.

Prepaid car rental does not always include everything eg local taxes and some insurances, one way drop off fees etc.

The speed limit on motorways is 70mph and there are speed cameras everywhere. It doesn't matter what the other idiots are doing.
If you were irresponsible enough to drive at 80 just after a long flight, I rather hope that you get a fine.

This is a council policy to reduce car traffic.>>>

Brighton is vehemently anti-car. It has Britain's only Green MP.

<<If you were irresponsible enough to drive at 80 just after a long flight, I rather hope that you get a fine.>>

Baa Humbug! Its more dangerous not to keep up with the traffic!

<<If you were irresponsible enough to drive at 80 just after a long flight, I rather hope that you get a fine.>>

<<Baa Humbug! Its more dangerous not to keep up with the traffic!>>

Absolutely - most people drive on motorways at 75-80mph in complete safety (the UK has one of the lowest fatality rates on such road types in the world). And there aren't cameras everywhere on motorways, just average speed cameras with lowered speed limits in roadworks, and very occasional cameras elsewhere. There are marked and unmarked police patrol cars who are likely to pull you over if you go over 75-80, or drive stupidly.