The regulations regarding radars used for SRAs are contained in CAP 670. In general;
11.1.1 When used for surveillance radar approach (SRA) purpose (i.e. primary only), the
accuracy shall be better than 1 degree of bearing and 55 Metres, + 5% of target range
(365).
11.5
Rotation Rate
11.5.1 The effect of rotation rate on system performance shall be defined and justified (451).
11.5.2 A primary radar providing the positional data for the following services shall rotate at
the following effective minimum turning rates:
a) General TMA Zone and approach work, a rotation rate of 5 RPM (452).
b) SRA to 2 NM, a rotation rate of 10 RPM (453).
c) SRA to 1 NM, a rotation rate of 15 RPM (454).
d) SRA to 0.5 NM, a rotation rate of 20 RPM (455).
Here is the address of the CAP 670 document on the CAA website;
www.caa.co.uk/docs/33/cap670.pdf
Hope this answers your question