My opinion as a self employed mechanic (ex Toyota ,Mercedes,jaguar, bmw) is that national tyres are doing charity work at that rate, put it this way they are not using a quality oil, not at that price.
An oil filer would cost me in the region of £5 or 6 quid +vat so might retail about £8 or 9 + your vehicle takes 4.7 litres so say 5 litres of high quality fully synthetic retailing at around £10 a litre + so that's around 60 quid ish for arguments sake, then an hours labour at around £45 to 50 + screen wash etc so say £140 ish inc vat for good reputable garage to do it.
Note; oil filter media is made to be comparable with the oil designed for that engine, using the wrong oil can cause this to become brittle and break up,this is really only visible on paper element insert filters. I have come across this on 3 occasions on servicing new customers cars.
Conclusion avoid national tyres like the plague,use Lexus for the minor services until u find a reputable garage to take on your car, and don't be afraid to ask important questions like what make and spec of oil are they using. A good quality oil is the best mechanic u will ever get.
The spec you req is 5W-30
GM DEXOS 2
MB229.01
BMW LL-04
VW 502.00/505.01
ACEA A3/B4
ACEA A3 low saps
Regards Shaun