You can put up your bean trellis if you fancy, no probs......one job done.
6ft for runners and climbing french beans, the height of your peas very much depends on the varietie you choose, some grow tall and some only a couple of feet, so decide which ones to grow first
Don't forget that you can also dig a bean trench and fill with kitchen waste over winter ready to cover and plant up with your runner beans. We did this last year and have had so many runner beans we have had to give them away!
We spent the winter doing the landscaping bit - marking out and preparing beds, clearing grass/weeds, putting up posts and stretching wires for training espalier trees, laying down weed suppressant and topping with chipped bark.
Are you planning to incorporate a tool store or similar into your plot? I know it uses valuable space up, but it is great to have somewhere to have a brew!
My other recommendation is to speak to other plot holders and find out what works on your site. Our site was originally used as an onion field before being converted to allotments after WW2. As a result, the ground has white rot resident and so you can only grow onions and garlic in raised beds. One end of our plot is free draining (aka rock hard after April generally) and the other end gets water logged. This means we ended up moving rhubarb and globe artichokes when we discovered this as they were planted in the drier area.
gavinjconway, I am dead jealous of your 20m x 10m plot!
We took over our 5.5 rod plot in June 2010 and have now run out of space! It is still over 80% planted up at this time of year - the gaps where we cleared the courgettes last week ready for garlic to go in and have got to clear the celery ready for the onions this week. We have actually reduced the width of the paths this year since plotting out the original design so we can grow more!
Despite my husband and I being experienced gardeners, the allotment don't give full plot sizes to new plot holders - you are only allowed a half plot. Never mind, some is better than none!