I have a new world gas cooker bur I am finding following recipes cooking guidelines results in undercooked bases of i.e. scones, fruit pies, or Xmas fruit loaf. When baking blind, the top of food looks cooked but the bottom is soggy and uncooked. I tried changing position of shelves and cooking longer on lower heat, but my normally good baking is no longer.
On many gas ovens, the calibration of oven temperature is fairly slack - the manual for mine says it can be off be 30 degrees either up or down. Invest in an oven thermometer, preheat your oven until it shows the desired temperature, and see if this gives you better results.
I have a new world gas cooker and have found the same problem. I did what James McLeod recommended and bought an oven thermometer and did find the results quite surprising. If I set the gas mark 4 from the off, it took half an hour or more to heat up - and higher temperatures even longer. I now set it to gas mark 9 until it has reached the desired temperature and then turn it to the required setting and it retains its temperature as it should. Obviously all models are going to act differently but I've moved the thermometer around the oven and it seems to heat quite evenly too.
Don't quite see why someone has down voted you? Anyway...
Strange that your tops are cooking while your bottoms are raw? Is it top heated?
I've had a similar issue but the other way round trying to cook scones, Yorkshire puddings and shortbread in a gas oven. The bottoms would burn while the tops were raw. I found the best fix for me was to put an empty tray on the bottom shelf and then cook directly above the tray on the upper shelf. My idea was the bottom tray would stop the direct heat hitting the bottom of my cooking trays. Resulting in a more controlled heat all over my produce instead of it being directed right at the bottom. In your case it might be worth putting a tray on the shelf above your food.
Also it is worth noting where the thermostat is in your oven. If I remember correctly the thermostat in the oven I was using was in the top where all the heat was coming from the bottom. This meant if I had placed my trays near the edge the heat wasn't getting close to the thermostat meaning the oven would keep blasting heat out obviously over doing the bottoms. If you are inhibiting heat getting to your thermostat in any way this could also be causing you issues.