Polytunnel Interior Design

Depends on your soil. If it's OK use it - you may need some boards to keep the soil off the path. If you have to import soil it might be better to put boards all round the beds and use boards to walk on rather than raised beds - more soil usage.
At some point you'll have to change the soil a bit so I would leave it as open as possible for digging and barrowing.

Thanks Guys

Our "poly tunnel" ( aka large greenhouse, aka dutch greenhouse ) was very wet ( during dodo summers, never mind winter! ), we decided to put drainage in rather than raised beds as it made rotavating far easier

For raised beds, every inch is an inch above your water table

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just erected a 30 foot by 14 foot polytunnel and as season is rushing on I have planted direct in ground for now and all looks to be OK. However as PT is a tall one I am going to put in 4 inch timber edges as sides and form slightly raised beds. Splitting width into 3 foot bed, 18 inch path, 5 foot bed, 18inch path and 3 foot bed all full length except the centre bed shorter at end when paths link and reach doors that open inwards. Seems to be the best use of growing space but still allow ease of movement and tallest plants to go at centre of PT. Also allows crop rotation bed to bed and end to end. Paths in wood chips on weed fabric but at doors will be paving slabs.
Not yet committed to any of this so comments welcomed.
R

To be honest I wouldnt waste polytunnel space on lettuce, they are easy to grow under a cold frame (unless you do want commercial harvests).  Theres many more plants that will make all this effort more worthwhile