If you are coming from North Wales are you planning to stop en route? Either way you'll need to file a GAR 12 hours before departure and 12 hours before return and a flight plan from your final departure point from the UK.
You can contact Plymouth Ops by phone (phone number is on the legend of the CAA 1:500000 Southern Chart) to see if the Portland danger areas are active and if they are you can often get a Danger Area Crossing Service from Plymouth military (frequency on the chart legend too) if you fly at 5000 ft or above.
If you can't do that then contact Bournemouth Radar and route overhead BIA and then track parallel to Q41 which is almost direct to Alderney. You need to contact Jersey control about 10 to 15 miles from the zone boundary and they'll clear you in before handing you to Guernsey approach and then Alderney Tower.
It's never been difficult but now the zone is class D and not Class A it's even easier. We have a house there and will be there for the fly in so if you decide to go send me a PM and I'll give you contact details.