Where I live my signal quality is low for some of the MUX's until the changeover but ours changes late in the game next year.
A newe box might pick the signal you have up better nad not drop out as much. You can pick them up for £10 or £20 depending on the offers at Morrisons and probably similar.
I picked a £10 one up with HDMI out so I could scrap the large SCART cable.
They're not great and not like my TV built in one, but better than the old ITV/On Digital boxes and some of the other one's I've had. All the budget cheap one's are the same in side, just re-branded. Give one a go and take it back if it doesn't work.
If you have a dish on the side then you can use a FreeSat box and get the FreeSat channels. Probably your best option as long as you don't mind giving it a direction tweak if it's slipped or knocked.
e-bay sell the LNB's you'll need another wire ran from it for each box you connect it too, so may as well get a 4x multi LNB
There are also 3 different types of Ariel and what you need will depend where your house is.
Some may need the one with many 'fins' Class 1, but are a bugger in the wind to get a strong reception as they move out of alignment easily, pidgins are another thing that must be shot

.
Some might need the good old less sensitive to movement one's, Class 3. Best get a trusted pro to put it up though. Around me it changes depending on where you street is and the hills. All due to being near the edge of the reception.
Though if your switch over is soon then wait it out.
This website
http://www.ukfree.tv/
is the best for info I've found. Tap in your postcode and you'll see all the details of you transmitter and works/problems. Also looks like they have more stuff now

Not read it for a while.
Explanations about all sorts there.