Hmm, three quid from China or 30 quid from
MTMC in Yeovil? Tough call.
One will take a month, may be stopped in customs and might be poor quality. If there is a problem, you have wasted all that time and are no better off at the end of things. Realistically, if it's not right, you are back to square one, minus a bit of cash and a lot of time.
The other will come from a reputable family firm, whom you can talk to in English on the phone, and who know their business (spare parts for tools) really well. You will get your parts by the next post that's practical. The price reflects the stockholding they carry to deliver that service.
Alternatively, might this be an opportunity to invest in a better quality, 1/2" collet router? I have a couple of small Bosch routers and suck my teeth over the price of their collets. And the ones I have, admittedly 1/4", don't work half as well as the Elu/Trend/DeWalt collet design - you either tighten excessively or risk the cutter slipping and chattering. The 1/4" collet for my big Trend T11 is pretty bomb proof. It has done a lot more work than the little machines but still grips correctly. And, being in the table mostly, it probably has more cutter changes than the small ones...
I wouldn't presume to tell you what to do, but I tend to buy from Miles Tools.