I've used PCBtrain (
https://www.pcbtrain.co.uk/quote-and-order-pcb/) - part of Newbury electronics, and they seem pretty damn good qality. 5-15 day lead time. They do a 'PCBexpress' with a 1 day turn around for designs without soldermask or silk screen.
However, for volume, and if time is not of the essence, then nothing really beats foreign companies like Golden Pheonix (never used em), or Olimex (used em once). I havent' seen he prices for bare single sided boards - as most manufactureres process for at the very least, double sided, PTH, solder mask and silkscreen on one side. Another option would be 'batchPCB' from sparkfun. These again would most likely have soldermask and sikscreen as standard ad I doubt it would be any cheaper to not have these options.
With no holes or via's either, sounds like a really basic board... something one could do at home perhaps? For 100mm x 15mm dimensions, 10 of these boards would fit on eurocard (160mm x 100mm). So you're looking at only *really* etching 5-10 boards, and then cutting them up. Worst part abou DIY boards is drilling, and the lack of plated through-holes/via's for double sided designs - your requirements completely negate both of these.
That said, even with basic designs, after 10 boards+ it quickly becomes far more economical to use a fabhouse.
Aside from the four companies I've mentioned (PCBtrain, Olimex, GoldenPheonix, BatcPCB) thats all I got :/
Update: Just did a quick quote on PCBtrain. For 50 boards, 15-day lead time, single sided, immersion silver - £143.33 ex VAT. Sounds like thats around £3 per board. £231 for 100. Thats actually cheaper than a recent order I did for 6 (!!!) boards with smaller dimensions, with a 5 day lead time.