oh right.... but can you avoid it? I think trains from that part of the country enter Paddington and to get to Gatwick you go via Victoria. Which is easily done by taxi as opposed to lugging to through the tube.
Yes, if you're traveling from Paddington to one of the other stations, definitely go by taxi rather than on the tube. Luggage and the tube do not go together!! Trains from where I live enter Paddington, and if I need to get to Waterloo (for the Eurostar) I always take a taxi. It's so much easier and less stressful.
As for train travel, I'm a huge proponent!! I always take the train down to visit my bf -- about an 8-hour trip in all. I always have a biggish suitcase as well as a carry-on. No problems at all. The trip involves two changes, but they're both easy -- there are always lifts at stations, even some of the smaller ones. Although, often at the smaller ones, you don't need to go "up and over." I've also taken trains to visit friends in London and that's easy as anything as well. If you have to connect in Reading, it's a breeze. And in all the time I've been doing it, I've never had a train that was late, I've never missed a connection, etc. I love the train! It's relaxing and way way way less expensive than driving!
both trainline and
www.qjump.com are good for booking trains. I always use qjump and get excellent deals -- try and book approximately three weeks before you need to travel. That seems to be the magic number.
Did I mention that I love the train!!?