Jezza, if you're replacing the camshaft and followers you'll need to set the preload on the (followers) hydraulic lifters. It's involved, being tricky for the home mechanic to measure and requiring shims under the rocker shaft pedestals to make any adjustments.
You can put everything together, measure the preload on each lifter and if you're lucky and they're ALL within tolerances (0.020" to 0.060" from memory) then you're set. If not you'll need to order a shim set from UK suppliers.
Last time I did it, even with reco heads, all new rocker shafts, cam and lifters, preloads were out - had to go new rockers and fit shims to get it right. Even valve wear where some of the valves have recessed into their seats and thus increased their protrusion above the top of the guide can send their lifter preload out of tolerance.
If you don't ensure preloads are within tolerances you risk noisy tapping lifters or worse, some riding valves that don't seat fully/long enough and burn out.
There are a few sites that illustrate and explain the procedure. I found using the extension arm of an electronic vernier caliper the easiest and most acurate way to measure preload.
