Unfortunately there is no definitive answer to your question and anyone who gives you one is likely to be talking porkies. The only way to find out is to get a pad and a paper and write down each and every airline that you want to work for when you are qualified. Then contact each and find out who they hired in the say last 6 months and what their backgrounds were. Getting that information will be like finding hens teeth.
Having said that here are my thoughts:
(1) there will always be chief pilots/recruiters who think that the sun shines out of Oxford, Jerez and Cabair. Mere mortals who went anywhere else will come a sorry 2nd to anyone from the above. The only chance of getting into these airlines is via the back door so to speak by getting a job elsewhere and proving yourself via your 1000 odd hours on jets etc.
(2) having said point (1) where you trained is down the list of what an employer is looking for. The key ingredient to me is having a network. If you just happen to know training captains/recruiters/daddy works there etc then have a think about how much better your chances are going to be of getting that first job ahead of someone who has mastered mail merge on MS Word and fired off 100 cv's and covering letters and more than likely sent them to the wrong person in anycase.
(3) lets say for arguments sake you save £5-6k by going stateside. Lets assume you have this cash burning a hole in your pocket. What if you went and hour built twin time in the US and came back with 75-100 hours total including your IR time. Most of your peers would have 25 hours max so your already ahead of them.
(4) consider what the smaller airlines/charter outfits are looking for. Take an example of say Loganair. Would they be interested in a guy who has 250 hours, lives in [insert big city here] but has seen Scotland on the weather reports. Someone like Loganair who would be pretty much representative of the smaller outfits is after someone who has maturity and will stick around. Its likely that they will want someone who is local or at least has ties to the area they are hoping to work in or in the absence of this at least have proven that they are upwardly mobile and have no problem adjusting to a different set of circumstances. In other words mummys boys need not apply.
The overall point I am trying to make is that where you trained is only a small factor in whether you would get called for interview and secure a job there is so much more to it and you need to look at the overall package rather than just the training element. My advice is concentrate on building that network up as it is contacts that will get your cv onto the right desk at the right time rather than rely on a bit of luck from mail drops.