Going through lots of Petrol, also a smell

I'm new to all this. Passed my test earlier in the year.

Recently my car sometimes smells of petrol on the inside and it's quite strong at times?

Also I put nearly 20 in the past 24 hours. And now my light is flashing...
Put £5 in this morning and done about 5 miles maybe a little more and as I say it's flashing....

Any help would be great!
I've a Vauxhall Astra. 07 Plate. TwinPorn. 1.6.
About 45 - 50 miles per gallon.