Hi and welcome to the forum, I've found some info on your receiver and it seems quite a recent model, so I'm unsure that new firmware would be beneficial. You need to give more information on the rest of your equipment, dish size, motorized or not and if fixed which satellite it might be pointing to. I'm guessing that it may be pointing to 13°E Hot Bird, but if you can name some of the channels you are getting it will help. Are you French or from the UK?
I live about 90 mins to the East of Rennes incidentally. If you are in France you have three choices. 1) Hotbird does have French channels on some transponders, but possibly not the ones you want. www.lyngsat.com will give you a list of them. Astra at 19E has maybe a couple more but again they are probably not the ones you prefer. 2) With what you already have try moving the dish over to the Atlantic Bird positioned at 5W.
This will give you the main four French channels, plus a couple of others and a few radio stations. 3) If your maison has a tv aerial (most regions actually have more than one banded aerial giving a broad frequency scan), try using the tv tuner to search for those coming from your local transmitter. They are broadcast in SECAM (L) though, so you will need a French compatible tuner and colour system. Just to affirm what CH and Rolfw have said: Rennes does have a Digital Terrestrial transmitter, located at St. Pern and it seems a quite powerful one, so if you have a clear line of sight with your aerial that could be a good option. I'm assuming that you have a monobloc lnb, so moving the dish to 5°W (where a lot of French dishes do point, most of them a legacy from analogue days) would rather waste the second lnb, unless perhaps you used it to watch programmes from a sat nearer to 0°, but that may not be possible.
You could always swap the monobloc for a single lnb if you wanted to stick to 5°W. That particular satellite is very strong and you should have no problems picking up any of those mentioned in posting with an 80cm. I certainly got good results with a 60cm dish. When you say you haven't 'found' Astra, have you selected that satellite on the receiver database and asked it to scan for channels?
Good Luck anyway Pete.
Hola gracias por leer este mensaje y deseo saber como configurar un Tboston. He leido el manual pero no lo. Y tengo un Tboston DVB 4500 New Usals lo tengo.