Take the pipe off the inlet side of the fuel filter head, and hold the end of the pipe as low as you can with a container under it to catch any fuel. you should get a free flow of fuel, if not, blow down the pipe, it doesn't taste too good but should clear any blockage without splutting the tank!! If you block off any breathers and blow down the pipe you should definately get a good flow of fuel, be careful not to get a mouthful.
It's very unlikely that the new filter is duff, it sounds like an obstruction in the tank pickup. Hence the checking of free flow from the tank. I've found pick ups blocked by swarf from when the tank was made, to dead flies and spiders. Problem is worse when refuelling out of cans rather than from the pump.
Check free flow first then go from there