With load carrying equipment, you might want to approach your solution(s) based on several important factors:
¤ What environment will I be in?
¤ What is my body type? (Height/weight/build)
¤ What type of scenarios do I need to access the mags in? (Open terrain patrolling/hunting? Riding in a vehicle discreet? Attending high-volume courses involving lots of movement East or West of the Mississippi? Helo hog-hunting?)
There are several generations of load-bearing gear and different approaches with each one. We can start with belt-based kit, which is historically rooted in 1800's and earlier military wide belt systems that maintained dominance in conventional armies through the 1990's, where they were finally displaced by modular systems. The benefits to belt & suspender systems is that they can be relatively lightweight, and offer the most breathing room for your chest and back. Modern large padded belt & suspender systems with MOLLE/PALS webbing on them are a huge leap in comfort and capability over last century models, and many modern gear makers have offerings based on them.
SAS Kit that would support the L1A1:
Modern Belt Kit with Suspenders:
http://soldiersystems.net/blog1/wp-content/uploads/2011/05/TT-Battle-Belt-Small.jpg
The next type is the AK chest harness variants. There are a lot of great offerings and they are simple, relatively snag-free affairs that also work really well with wearing a rucksack or 3-day pack. In hot weather or intense movement, they can suck for overheating, since so much of your chest is covered, so the models with spacing and mesh on the backface help mitigate this issue. I like chest rigs that are integrated with a hydration unit on the back, with routing through the suspenders that is concealed and snag-free, that also doesn't dig into your upper & middle trapezius group.
http://www.tea-and-medals.co.uk/images/equip_chestrig_front.jpg
Then you have your various vest types, like Rhodesian & South African, the widely imitated Eagle TAC-V series, US LBV types that were improved upon greatly by the Squeals, and one of my favorites-the British DPM Assault Vests with mesh, internal map/doc pouches, with plenty of utility and mag pouches.
https://www.dragonsupplies.co.uk/u_images/1226001569_LG.jpg
For your pouches, you need to determine if protecting the mags from foreign debris is more important, or quick access is your priority. For me, when I'm in high dust/wind environments or when I expect to do a lot of crawling no matter what environment I'm in, traditional enclosed mag pouches are the way to go. Right now, open-top fast access mag pouches that are really designed for fairly sanitary short-duration mission profiles are popular, since you can access the mags much quicker for reloads, and everyone wants to be kitted out like a JSOC SMU kicking in doors in the middle of the night after being infil'd via MH-6, but the reality is that that mission profile isn't really appropriate for most people to model their load carrying configuration after.
What you can do is have most of your pouches fully enclosed if protection is important, then have one or two open-top pouches for your speed reloads.
For 7.62 NATO 20rd mags, I like to be able to use a common pouch that will accommodate both 30rd 5.56 M4 & battle rifle loads so I don't have to re-configure anything. Others use a dedicated kit for each. Paraclete had a cool system where you could zipper off modular panels that are also MOLLE, and keep your load-bearing base kit the same, and allow quick configuration of your set-up depending on the weapon you were carrying, while leaving your hydration, commo, navigation, survival, & med kit unmolested.