SQL Server 2008 :: Summarizing Transaction Data Removing Nulls?

I have two tables one list changes of hospital ward and one lists changes of consultant doctor. These can change independently ie a ward change can occur without a consultant change and vice versa. I want to summarise these changes to give the status at each date_serial value.

create table #temp_ward_stay(date_serial bigint,ward_id varchar(10))
;
insert into #temp_ward_stay
values
(201501021200,'W1'),(201501031201,'W2'),(201501091200,'W3'),(201501161200,'W4'),(201501161201,'W5')(201501271200,'W3'),(201502101200,'W5')
;
create table #temp_consultant_episode(
date_serial bigint,
consultant_id varchar(10))
;
insert into #temp_consultant_episode values
(201501021200,'C1'),(201501031200,'C2'),(201501031201,'C3'),(201501091201,'C4'),
(201501121200,'C3'),(201501301200,'C6'),(201502111200,'C6'),(201502111201,'C7')
;

If I use:

select date_serial,consultant_id,null as ward_id from #temp_consultant_episode
union
select date_serial,null as consultant_id,ward_id from #temp_ward_stay

I get:

date_serial ward_id consultant_id
-------------------- ---------- -------------
201501021200 NULL C1
201501021200 W1 NULL
201501031200 NULL C2
201501031201 NULL C3
201501031201 W2 NULL
201501091200 W3 NULL
201501091201 NULL C4
201501121200 NULL C3
201501161200 W4 NULL

[code].....

whereas what I actually want is:

date_serialward_idconsultant_id
201501021200W1C1
201501031200W1C2
201501031201W2C3
201501091200W3C3
201501091201W3C4
201501121200W3C3
201501161200W4C3
201501161201W5C3

[code].....

I can see how I could remove the nulls where the date_serial values are the same:

select ce.date_serial,ward_id,consultant_id from #temp_consultant_episode ce
join #temp_ward_stay ws
on ce.date_serial=ws.date_serial

but I can't see how to move forward from here.