One point to the OP: if you have an older van the aerial cable inside will likely be of the brown type that we used at home 30-40 years ago (although in caravans often in a white sheath.) The braid on the outside of the central core is often just some strands of wire wound loosely around the core insulation. As I found out the hard way this can cause serious problems with DTTV.
When we had a Bailey Pegasus Majestic S5 on one occasion by wife complained that the picture was pixelating as I moved around inside the caravan. As a test I put a tail of modern foil-screened cable (CT100 at that time) directly from the aerial amp output to the TV. Bingo, fault resolved. The problem was that the cable inside the caravan was picking up signal directly from the transmitter and was interfering with the 'proper' signal being sent down the cable from the amp.
When we got home I replace all the internal aerial wiring with CT100 (would now be PF100 or WF100) and we never had a problem anywhere again.
Cable, connectors (in packs of 10) and anything else are cheap from Toolstation or Screwfix - NEVER buy from a DIY shed or (especially) from a caravan dealer!!