Barton village hall on a Tuesday Morning Blossoming Buds in Kirkham have a Weighing scale too x
Theres a few drop in clinics around preston, you can check the health visitor site for info, I know the one closest to me I went thursday afternoons Looks like fridays closest is leylands https://lancsyoungpeoplefamilyservice.co.uk/child-health-clinics/
Google 'child health clinic preston' and it will show you all of the clinics in Lancs. I think the only place that does it on a Friday is Leyland and Blackburn or Accrington though x