Lots of questions about timer sections and joist hangers...

I plan to put new joists in my loft (sitting on raised wall plates, so I
have a nice strong floor that doesn't interfere with the trusses), but due
to the dimensions etc, the last joist will run parallel to the gable end,
about 800mm away. The joists are 2" x 8" on 400mm centres as per BCO span
tables.

What I am planning to do is run some 800mm sections of 2"x6" (2" smaller to
avoid hitting the joist of the last truss) between the last joist and the
gable end wall at 90^ to the joist/wall, sort of like a noggin arrangement.
I plan to use speedy joist hangers
http://www.screwfix.com/app/sfd/cat/...60964&ts=39429 to attach the
800mm sections to the last joist, but I am not sure how to attach the other
end to the gable wall. The way I see it is there are 2 options :

1) use hangers like this
http://www.screwfix.com/app/sfd/cat/...95710&ts=39580 directly
bolted to the gable wall. If I went down this route, should I use expansion
bolts, or just some 3" x 12 screws into a good anchor?

or

2) Use something like expansion bolts to bolt 2"x8" joist sections to the
gable wall as a batten, then use speedy hangers of both ends of the 800mm
sections. If I were to do this, how far apart should the bolts into the
gable end be?


The second question I have is about loading. The joists are on 400mm centres
and that fits with the BCO span tables. If I were to do this thing with the
800mm sections, given that one end is bolted to the masonry in some way, is
the final joist considered to be taking more load as the next joist is 800mm
away (although it is actually the wall?) I was thinking that because the
final "joist" is in fact the gable wall, that it would the best place to put
the heaviest things.

The third question I have is about the 800mm sections. As their span is only
800mm (wall to final joist) would 400mm centres be sensible?

The fourth question relates to the loft hatch opening which has a new joist
either side which are 800mm apart. To support the floor across this span
(chip boards seem to require supporting every 400mm) and I better off :

(a) putting a proper joist in that runs between the wall plates and a pair
of noggins just before/after the loft hatch opening

or

(b) Putting in a series of 2" x 6" noggins between the new joists either
side of the loft hatch.

My instinct here is (a), because at least one end of the joist would be
transferring weight to the walls, even though the other end is transferring
load to adjacent joists via the noggin. With arrangement (b) all the weigh
in the 800mm void between the joists is transferred to the adjacent joists,
so I essentially have joists on 800mm centres.

Thanks in advance for any thoughts on this...