It's a hot, hot day in Portugal… and 'Spinal Tap' is happily cruising down the highway. The windows in the van are down, and the bikini and boardies are on. We're heading south, towards the cool water of Cascais, a beach town about twenty minutes west of Lisbon.

According to the GPS, we have a good 250kms before we can cool off. Thankfully, it's an easy drive. Most of it runs along one motorway. It's a toll road, but that's not a big deal. We've paid a few tolls on the trip so far and they've never been more than a couple of euros.

Three hours later, we're finally pulling into Lisbon. The weather is still steaming. Little do we know that we are about to become even hotter under the collar.

As we reach the toll booth, we're fumbling with the small change in the ashtray when we when spot the fee for the car in front. 16.50 euros.. ouch! We're still laughing at the poor guy when we pull up to pay our ticket.

But our smiles quickly disappear. Big red numbers flash on the screen in front of us… 33 EUROS! And that's when the swearing starts.

"What do you mean it's 33 euros!? The car in front was half that?" Politely, but firmly, the attendant tells us that we are a Class B vehicle and not a Class A. Despite blocking up the traffic for a good two minutes while we argue, he won't be swayed. It's 33 euros or the toll gate stays down.

Here's what we learned… the hard way.

Never pay your tolls at the manned toll booth. Always go through the automatic lane. It lets you choose what class vehicle you are. Class A is half the price of class B. Don't worry if you don't have the exact amount, the machine accepts credit cards and gives change.

If you want to avoid tolls completely, all of the European maps list the toll roads. If you have a GPS, it's even easier. Just choose 'No tolls' and it will set you a fare-free route.

Even though we got stung, the good news is… it was worth it. 'Spinal Tap' is parked overlooking a stunning beach just outside Cascais. It's been a long, hot, frustrating day, but a quick dip in the ocean is enough to cool us off… in every sense.

We've got a van full of food, and the local surf club operates clean showers and toilets for about one euro. For the next few days, we're staying put and saving cash. No road tolls, no camping fees, no fuel… nothing.

WICKED TIP… The AA in Britain lists all of the major tolls for Europe on their website. Print out the countries you are going to before you leave. Then, work out if it's really worth driving the extra distances to avoid paying the tolls. There's no point adding 100kms to your trip if the toll is only 1 euro.