The idea that we have a sufficient quantity of accurate data about Chernobyl to make sweeping claims about its impact on people living there, including how many died as a result, is frankly idiotic. We do not and never will have such data.

Okay, I'm just going to set your claim against the introduction to the report (http://www.unscear.org/docs/reports/2008/Advance_copy_Annex_...) referenced in the BBC article.

There has been an unprecedented effort by the international
community to assess the magnitude and characteristics
of the health effects due to the radiation exposure
resulting from the accident. As early as August 1986, a
widely attended international gathering, the “Post-Accident
Review Meeting”, was convened in Vienna. The resulting
report of the International Nuclear Safety Advisory Group
(INSAG) contained a limited but essentially correct early
account of the accident and its expected radiological consequences
[I31]. In May 1988, the International Scientific
Conference on the Medical Aspects of the Accident at the
Chernobyl Nuclear Power Plant [I32] held in Kiev summarized
the available information at the time and confirmed
that some children had received high doses to the thyroid. In
May 1989, scientists obtained a more comprehensive insight
into the scale of the consequences of the accident at an ad
hoc meeting convened at the time of the 38th session of
UNSCEAR [G15, K25]. In October 1989, the former Soviet
Union formally requested “an international experts’ assessment”
and, as a result, the International Chernobyl Project
(ICP) [I5] was launched in early 1990; its conclusions and
recommendations were presented at an International Conference
held in Vienna, 21–24 May 1991 [I5]. Many national
and international initiatives7 followed aimed at developing a
better understanding of the accident consequences and in
assisting in their mitigation. The results of these initiatives
were presented at the 1996 International Conference on One
Decade After Chernobyl8 [I29]. There was a broad agreement
on the extent and character of the consequences.

...

The objective of the present annex is to provide an
authoritative and definitive review of the health effects
observed to date that are attributable to radiation exposure
due to the accident and to clarify the potential risk projections,
taking into account the levels, trends and patterns of
radiation dose to the exposed populations. The Committee
has evaluated the relevant new information that has become
available since the 2000 Report, in order to determine
whether the assumptions used previously to assess the radiological
consequences are still valid. In addition, it recognized
that some issues merited further scrutiny and that its
work to provide the scientific basis for a better understanding
of the radiation‑related health and environmental effects
of the Chernobyl accident needed to continue. The information
considered included the behaviour and trends of the
long‑lived radionuclides in foodstuff and the environment in
order to improve the estimates of exposure of relevant population
groups, and the results of the latest follow‑up studies
of the health of the exposed groups. The effects of radiation
on plants and animals following the Chernobyl accident are
discussed separately in annex E, “Effects of ionizing radiation
on non‑human biota”. Other effects of the accident, in
particular, distress and anxiety, and socio‑economic effects,
were considered by the Chernobyl Forum [W5] but are
outside the Committee’s remit.

The Committee, in general, bases its assessments on
reports appearing in peer‑reviewed scientific literature and
on information submitted officially by Governments in
response to its requests. However, the results of many of
the studies related to the Chernobyl accident have been
presented at scientific meetings without formal scientific
peer review. The Committee decided that it would only
make use of such information when it could judge that the
results and the underlying work were scientifically and
technically sound.