I've heard that the price per barrel is going up because of the current trouble in the middle east, but also that the government are planning to add 5p a litre in the next budget. To be honest, boycotting 1 or 2 brands of petrol wouldn't lower the cost. For that to work literally no one in the country would be able to use those brands, that wouldn't happen so BP and Esso would put their prices up to compensate for the lack of sales, and the other companies could follow suit to stay close to the competition. The reverse of what we want to happen.
At the moment, the only thing out there that seems to be doing anything and going about it the right way is
http://www.fairfueluk.com/ who are working with Quentin Wilson to try and:
1) stop the rise in april
2) get the promised fair fuel stabiliser put in place to bring the cost of fuel down
Quentin and FairFuelUK have already visited downing street once already (which did get some news coverage) and are planning to go back soon to deliver the first batch of signed petitions. If you want to see the price go down, the best chance we have is this. I know a lot of people think that petitions don't work, which may well be true, but it only takes 1 minute to fill in, so is worth a try, and as this one has the involvement of a TV personality (Top Gear & 5th Gear, an more) it is likely to generate more media coverage and therefore more support. So if you want to help, 5 minutes is all you need to
1) sign the petition
2) write to your local MP showing your concern for the price and support for the cause
Details of both things can be found on their homepage.