It's so simple. All you need to do is just measure along the side of the caravan with a tape measure and see what obstructions there are such as a side window, an upper marker light, a 240 volt mains electric flap, a side service ot toilet cassette door,etc. and jot down the lengths respectively. Then you can decide which one is suitable out of the selection available which are usually 260, 330 or 390 etc.
Thankyou for your replies but the reason I can't measure it is because it is in storage over 200 miles away. I just thought some one may know the measurement. Thanks anyway.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.